MathPuzzle.com

Next talk: Thursday, October 22, 2026

Sporadic Similar Triangles

Thursday, October 22, at 11 AM Chicago time (CDT). Watch on YouTube.

I'll be talking about sporadic similar-triangle dissections, the new substitution tilings they lead to, and recent recreational mathematics. There are two movies, with almost a thousand slides between the movies and the rest of the talk. Stop by to see the new tilings.

A Kepler right triangle repeatedly dissected into similar triangles

A right-triangle substitution with 856 triangles at stage 14

The cube-root family: seven-, nine-, and eleven-piece triangle dissections

A rho014 substitution with 426 triangles at stage 14

Pictures from my talk preview. Click an image to see it at full size.

Mathematical Games: 2026

Monthly talks, with the newest first. 2023–2025 archive · Video playlist · My Staff Picks. Dates marked ‘Posted’ are Community publication dates.

Posted September 24, 2026 · Monthly talk

Filling Space with Similar Parts

How many ways can a triangle be cut into smaller copies of itself? This talk starts with tilings and solids that surround themselves, then moves on to self-similar dissections and some decidedly unusual triangles.

Community post and notebook · Watch the talk

Posted August 28, 2026 · Monthly talk

Colors and Combinatorics

How many regions do cuts make, and when does the obvious counting pattern fail? This talk mixes circle-cutting puzzles, graph crossings, and color with some recent mathematical news.

Community post and notebook · Watch the talk

Posted July 15, 2026 · Monthly talk

Square Packing

Packing squares sounds simple until a tilted square improves the answer. This talk looks at recent packing results, squared squares, and some connections with graph theory.

Community post and notebook · Watch the talk

Posted June 25, 2026 · Monthly talk

Integer Sequences

A sequence is often a clue to a counting problem rather than just a list of numbers. This talk includes the no-three-in-line problem, geometric patterns, and examples that can be explored with the OEIS.

Community post and notebook · Watch the talk

Posted May 25, 2026 · Monthly talk

Geology, AI and Recent Advances

This one takes a detour through geological time, with fossils, changing continents, and experiments in using AI to help prepare a presentation. There are also updates on graph crossings, packing, and the no-three-in-line problem. The notes are spread over four Community posts.

Community notes: Part 1, Part 2, Part 3, Part 4 · Watch the talk

Posted April 16, 2026 · Monthly talk

Space Groups and Filling Space

Crystals and space-filling polyhedra give the 230 space groups something concrete to act on. The examples use lattices and Voronoi cells to build shapes that fit together in three dimensions.

Community post and notebook · Watch the talk

Posted March 19, 2026 · Monthly talk

Pi, Circles and Spheres

A March collection of circle and sphere problems, with π appearing in several different roles. There are pictures, constructions, and puzzles to try alongside the calculations.

Community post and notebook · Watch the talk

Posted February 19, 2026 · Monthly talk

Games with Markov Chains or Intransitivity

What happens next can depend on what just happened. Starting with letter patterns in Alice in Wonderland, this talk explores Markov chains and games in which “better than” can go around in a circle.

Community post and notebook · Watch the talk

Games with Markov Chains or Intransitivity

Posted January 22, 2026 · Monthly talk

Two, Phi, Psi, Chi, Rho

The golden ratio has company. Powers of these five numbers turn up in triangles, polyhedra, and substitution tilings; the talk follows several of those connections through exact constructions.

Community post and notebook · Watch the talk

Mathematical Games: 2023–2025

Mathematical Games archive: 2023–2025: I've been hosting a series of monthly, hour-long talks about various subjects in the spirit of Martin Gardner's Mathematical Games series. My Wolfram Community page is here: Ed Pegg Jr You can see the Youtube links 1 and YouTube links 2. The sections below cover most of the talks I've given so far.
Mathematical Games: Mathematical Constants: Posted December 18, 2025. A fast tour of the “famous numbers” that keep showing up everywhere: π, e, φ, and friends. The talk focuses on where constants come from (geometry, limits, probability, optimization) and how to spot them when they are hiding in plain sight. Community post. Watch

Mathematical Games: Fractals: Posted November 20, 2025. Fractals in practice: self similarity, substitution rules, and complex sets. Part 1 · Part 2. Watch

Mathematical Games: Seven in Graphs and Geometry: Posted October 24, 2025. A seven themed tour through graphs and geometry, highlighting where 7 shows up unexpectedly. Community post. Watch

Mathematical Games: Knots and Crossing Numbers: Posted September 18, 2025. How to compare knot diagrams by crossings, and what changes when you simplify a knot. Community post. Watch

Mathematical Games: Unit-distance Graphs: Posted August 21, 2025. Graphs drawn with all edges the same length, and the combinatorial trouble that follows. Community post. Watch

Mathematical Games: Covering Sets: Posted July 24, 2025. Covering problems and minimal sets, with constructions and lower bound arguments. Community post. Watch

Mathematical Games: Measuring the Universe: Posted June 26, 2025. From Eratosthenes to modern methods, turning angles, light, and timing into distances. Community post. Watch

Mathematical Games: Polygons and Polynomials: Posted May 22, 2025. Geometry meets algebra: polygon structure that turns into polynomial identities. Community post. Watch

Mathematical Games: Famous Equations: Posted April 24, 2025. Equations that earned their fame and the ideas behind them. Community post. Watch

Mathematical Games: Game of Life Circuitry: Posted March 20, 2025. Building logic and computation inside Life using gliders, guns, and timing. Community post. Watch

Mathematical Games: Puzzles on a Square Grid: Posted February 21, 2025. Classic grid puzzles and local constraints that propagate across the whole board. Community post. Watch

Mathematical Games: 2025, Other Numbers and OEIS: Posted January 31, 2025. Year number puzzles and a quick tour of OEIS as a search tool for sequences. Community post. Watch

Mathematical Games: Diving into Cards: set, dominoes, spot-it, scrabble & more: Posted December 20, 2024. Combinatorics behind games and decks: Set, dominoes, Spot It, Scrabble, and beyond. Community post. Watch

Mathematical Games: Anagrams, Letter banks and Other Wordplay: Posted November 22, 2024. Wordplay puzzles where constraints are the engine: anagrams, letter banks, and more. Community post. Watch

Mathematical Games: Linkages: Posted October 24, 2024. Mechanical linkages that trace curves, with rigidity and degrees of freedom in the background. Community post. Watch

Mathematical Games: Ordering and Canonical Forms: Posted September 19, 2024. How to put objects into a standard form so duplicates vanish and comparisons get easy. Community post. Watch

Mathematical Games: Icosahedra and other polyforms: Posted August 15, 2024. Polyforms inspired by icosahedral symmetry, plus counting and classification ideas. Community post. Watch

Mathematical Games: Turing Machines: Posted July 19, 2024. The core model of computation, and why simple rules can still be universal. Community post. Watch

Mathematical Games: Linear Algebra Magic: Posted June 20, 2024. Matrix tricks, eigen ideas, and why linear algebra explains so many puzzles. Community post. Watch

Mathematical Games: Combinatorial Codes and Designs: Posted May 16, 2024. Error correcting codes, block designs, and finite geometry connections. Community post. Watch

Mathematical Games: Space-filling Curves: Posted April 19, 2024. Hilbert and Peano style recursion, plus what it really means to fill space. Community post. Watch

Mathematical Games: Hexagrammum Mysticum: Posted February 15, 2024. Six points on a conic and the cascade of lines and intersections they generate. Community post. Watch

Mathematical Games: Surfaces: Posted January 19, 2024. Surfaces by cut and glue thinking, with topology flavored invariants and examples. Community post. Watch

Mathematical Games: Configurations: Posted December 21, 2023. Point line configurations and the combinatorial rules that make some layouts possible and others impossible. Community post. Watch

Mathematical Games: Special Triangles and Tetrahedra: Posted October 20, 2023. Triangle geometry plus 3D analogs, with symmetry, extremal points, and constructions. Community post. Watch

Mathematical Games: Tetrahedral Centers: Posted May 19, 2023. Named centers of tetrahedra, with coordinate and symmetry based ways to locate them. Community post. Watch

Mathematical Games: The Hat and Other Tilings: Posted May 8, 2023. Aperiodic tilings and how local matching rules can force global structure. Community post. Watch
Mathematical Games: Algebraic Number Magic: Posted March 16, 2023. How roots, conjugates, and minimal polynomials turn messy expressions into exact values. Community post. Watch
Mathematical Games: Fun with Fractions: Posted February 24, 2023. Fraction puzzles and number sense shortcuts, including surprising identities and simplifications. Community post. Watch
Mathematical Games: Collection of Points and Lines: Posted February 17, 2023. Incidence geometry from point and line collections, with counting constraints and classic constructions. Community post. Watch

Material added 1 Jan 2026

NPR Puzzle and Welcome to 2026: I think the NPR Puzzle is mine this week. Related to that, 2026 = 1+2*3!*4!*56*7!/8!+9. For the puzzle, you'll need to find something simpler.
Tiling Facebook Group and Facebook Jail: Over at Mathematical Tiling and Tessellation, I run a Facebook group with currently 125,000 followers. However, after posting an image of Ford Circles, Facebook decided to ban me for a full ten days, the infamous Facebook Jail. Due to the fact that I could lose a whole bunch of stuff at any time, I decided I really needed to get my site operational again. There is other material on Wolfram Community as well, such as the 38-sided convex polyhedron that tiles the plane.


2026 New Year Puzzle: From George Sicherman, he sends a 2026 Puzzle.
Cracking the Cryptic: I had a sudoku in the famous youtube series Cracking the Cryptic with a puzzle I called Duplicate Bridge. I wrote it up with a Community Post.
Non Sequitur the Equitaur: I wrote an illustrated science fiction novel, Non Sequitur the Equitaur. The story is also at Royal Road. In all, the book has sold under a hundred copies, and I haven't gotten any fair reviews in over a year. If you'd like to help me out, reviews for my book will help me more than anything else. I expect to have the second book finished within a few months, and I also have an audiobook for the first book almost finished. I plan on changing the cover soon, so the first edition with this cover will be an extreme rarity. Imgur and other image sites have extreme restrictions, so I'll be storing images here.

Material added 27 June 2020

NPR Puzzle: The NPR Puzzle is mine this week. Think of a 5-letter animal. Remove the middle letter, and two opposites remain. What animal is it?
Heesch 4: Craig S. Kaplan‎: It seems appropriate to spend some of this quarantine computing coronas! Here's the smallest polyiamond with Heesch number 4, a 20-iamond.

Anagram: We're all in this together
=
We are still here tonight.
Puzzle Fun Magazine: A new issue of Puzzle Fun is out.
Proofs From The BOOK: Many titles like Proofs From The BOOK are currently available free from Springer.
PsiQuad 3-colorable: Stan Wagon has shown that my Psiquad tiling is likely 3-colorable.

A4 Paper: Here's one of those solutions that's so mathematically perfect that I can't believe that I'm the one that found it. All rectangles are similar to the outer rectangle, which has area 200. Theoretically, 50, 64, 72, 81, 98, 100, 121, 128, 144 can be added to get a similar rectangle with area 1058. I picked this set because there were lots of potential edge-matches, but I got forced to a solution where no edges matched.

Didrafters and Taco Chips: George Sicherman: The below shapes are the 13 didrafters. Arrange 8 of the 13 didrafters to make a solid rectangle. Then make nine convex shapes. Then add a few more pieces for the Taco Chips puzzles.

Food Menu: I found this food menu amusing.

Foster 084 A Graph: While at a meeting for making nice graph embeddings out of graphs that looked lousy, I made what is likely the first nice embedding for the Foster 084A graph.

Venn 7: Venn 7 from Andreas Gammel.

Extraordinary Conics: With five lines/points, find the conic.
Interstellar Blackboards: The Blackboards of Kip Thorne in the background of Interstellar.
1D CA Carpet: This 2D fractal can be made with a 1D Diagonal CA.

Unholey Deciamonds: Patrick Mark Hamlyn‎: The 444 unholey deciamonds in 37 congruent shapes. Took about 24 hours to develop piece tilability data for the BFS for this shape, and 43 minutes to tile the 37 shapes using that data.

Graceful Graphs: The first is the unique minimal heptic graceful graph. The next is a minimal octic graceful grace. The third is a graceful rook grid with all differences 1 to 48.

Conway Knot Problem: Lisa Piccirillo has solved the Conway Knot Problem.
Safety First: Things are getting safer here in Illinois ever since we went hardcore on it back in March.

Conway, Berlekamp, Guy: Soon after Conway, Berlekamp, and Guy signed this for me, Conway hunting me down. "Ed, we need to borrow our books!" So I handed them over. They met with A.K.Peters and Tom Rodgers to arrange for the second edition 4-volume set of Winning Ways. So long old friends. Remembering John Conway. Remembering Richard Guy and John Conway.

Me Berlekamp and Guy

Material added 27 Feb 2020

New Tetrad: Walter Trump has found a new tetrad.

Sparse Rulers Mostly Solved ||||.......................|....|...|...|...|...|...|..|..|: I solved sparse rulers and it's all written up in my blog article Hitting All The Marks. Sparse rulers allow the measuring of all distances up to length n. B. Wichmann almost completely solved the problem in 1963. From Wichmann's sparse ruler recipe, M_n - rnd(√(3 n+9/4)) can be shown to usually be 0 or 1 (the excess). The length 58 ruler at the top is conjectured to be the longest sparse ruler with fewer marks than a Wichmann construction, but no proof is known. Adding a single mark to the end of Wichmann's construction allows the building of excess-01 rulers for all lengths over 257992. My code found solutions for hundreds of difficult smaller lengths such as 1792, 5657 and 16617 to establish that excess-01 rulers always exist.

Orchard Problem: In a previous blog on the orchard problem I mention "If you do not like points at infinity, arrange 3 heptagons of 7 points to make a 4-configuration of 21 lines through 21 points." In the next paragraph I mention the record for 22 points. That record was beaten Dec 2019. This new solution is the 21 point 4-configuration with an extra tree at the center. How could I have missed spotting that?

Submarine Turmite: At github Turmites are many results on 2-D Turing Machines. One of them is what I call the Submarine turmite. Here it is at 7 trillion steps.
{{{1,2,0}, {2,1,0}, {3,4,0}, {1,1,0}}}

101 Enigmatic Puzzles: 101 Enigmatic Puzzles by frequent contributor Mark Wolf is now available at Amazon.

Material added 26 Jan 2020

New Heesch Tilings found by Craig S. Kaplan: Some new Heesch tilings. For more, see the Numberphile Heecsh video. Craig also made the Good Fences app.

vZome 7.0: vZome 7 is available for download, and also has a launch video.
Different Rectangles: Can a 3D object be made with different rectangles? Yes.

Star Polytopes: Nan Ma has been making excellent visualizations of star polytopes.
1161 Unholey Hendeciamonds: Patrick Hamlyn can divide these into 43 symmetric shapes.

Balanced Magic Square: If weights of the same amount are substituted for the numbers of each square, the balance point will be at the exact center of each square. The first is a magic square, the others are its 2nd, 3rd, and 4th power. 48 order-4 magic squares remain balanced under squaring, but this is the unique square to remain balanced with the 3rd and 4th power.

6-punch Triangles: There are 24 ways to put spots on the corners/edges of an equilateral triangle, with 1-sided rotational symmetry. They fit nicely into a hexagon with matching. With 2-sided rotational symmetry, there are 20 ways -- can they make an icosahedron with edge matching? Bryce Herdt: "First, each vertex must be surrounded by either 0 or 5 corner holes, and there must be six of each vertex. There are four tiles with no corner holes; these must share the six no-hole vertices, and can do so in one of two ways. Note the four tiles have twelve corners total. By the Pigeonhole Principle, we can say that at least one vertex belongs to two or more triangles. But since each vertex has only five neighboring vertices, then whether or not the two triangles just mentioned share an edge, there must be two triangles that actually do share an edge. Repeating this logic shows that three, then all four triangles with solid corners are connected in one tetriamond. This can't be the C shape, as that would make five faces with no corner holes, but the other two shapes are fine. With that fiddly part out of the way, note that in either case, the four solid-corner tiles form a single cluster with six perimeter edges and six internal edges in three pairs. These four tiles have six holes among their edges, and an even number of these must be internal, leaving an even number (two or four) for the perimeter. Now consider the six triangles with one corner hole. Call the edge opposite this hole the "base"; these bases ought to match up to the cluster's six edges. But three of these bases have holes, and three do not. There is no way to match the three holes to the cluster's even number of perimeter holes, QED."

5-touch hexominoes: Every hexomino touches 5 others, by Erich Friedman. I didn't know that was possible. At the link you can see how George Sicherman did it with pentominoes.

A perfect triangle dissection: Triangles of size 2-10 pack into a 16x18 rectangle perfectly.

Infinite Ammann Chairs: Infinite sequentially-sized Ammann Chairs can be packed into a rectangle.

No Shared Edge Dissection: At Triangle dissection, no shared edges, I have seven solutions. Are there others?

Pi from Menger: Squeezing Pi from a Menger Sponge worked out well, and was put into standupmaths.
Puzzle Box: The Puzzle Box series has a few dozen puzzles by me.
Screw Crossword: After making a demo on Ponting's Squares, I wondered how it might look like as a crossword.

Material added 12 Jan 2020

Plastic Pentagon: Let p=1.32472... be the root of x^3 - x - 1, the plastic constant. The points in the figure are pairs of triples (a,b,c) used in sign(k) sqrt(|k|) where k=a p^0 +b p^1 + c p^2. Numbers on the lines represent integer powers of square roots of the plastic constant. In 3D there is a 19 point powered clique set.

Every positive integer is a sum of three palindromes: Every positive integer is a sum of three palindromes, Javier Cilleruelo, Florian Luca, Lewis Baxter: arxiv.org/abs/1602.06208.
Biggest Little Polyhedra: Biggest Little Polyhedra. A talk I gave at the G4G conference based on the Demonstartion Biggest Little Polyhedron.
Heptahedra: The 34 canonical heptahedra.

Almost Perfect Tan Solution: This is a complete set of triangles with side 1 to 11, and the same triangles scaled up by sqrt(2). Just a small square hole remaining. Edit: George Sicherman: By the way, your 1..11 + 1q..11q can be done as a 20 x 38 rectangle.

Magic Areas: Magic square with areas.

Mondrian Square 26: A size 26 square divided into rectangles of area 18 to 24, each used twice in different orientations. As a puzzle, do the same with the 10x10 square.

51 points in 51 lines of 4: A 51 point/line 4-configuration. The equations of the points are the same as the equations of the lines.

tiling a rectangle with the smallest number of squares: Let f(m,n) be the minimal squares to tile a rectangle. Can an integer multiple be tiled with fewer squares? I give a few thousand possible examples.
Heilbronn 13: An improvement to a solution by Peter Karpov. My coordinates: {{0, 0.0992502414}, {0, 1}, {0.0879381177, 0}, {0.6551614146, 1}, {0.7485503739, 0}, {1, 0.4613325715}, {0.96481495015, 0.0876289126}, {0.0879381177, 0.6145067772}, {0.8969384849, 0.90254564724}, {0.3450133066, 0.90150725976}, {0.5001806186, 0.1492347859}, {0.7613458201, 0.4419966218}, {0.3284895496, 0.6333566986}}.

27 lines of 4: 25 points in 27 lines of 4.

New Yorker Error: This ad by Architectural Digest in the January 6, 2020 New Yorker magazine has a huge error.

Integer Partitions: Connecting Distinct and Complete Integer Partitions by George Beck has some nice new relations.
Square into 46 45°-60°-75° Triangles: A square can be divided into 46 45°-60°-75° triangles.

Mondrian Cubes: There are 11 distinct cuboids of volume 25 to 36 that can fit into a 7^3 box. Turns out they all fit perfectly in a unique way.
There are 13 distinct cuboids of volume 12 to 24 that can fit into a 6^3 box. Leave out the 1X3x5 and they all fit perfectly in a unique way.

Contiguous Partridge Tiling: George Sicherman: The monodom also has a contiguous partridge tiling (not reverse partridge)! These are hard to find.

Material added 2 Jan 2020

Colonel's New Year Puzzle: George Sicherman: You can download my 2020 New Year Puzzle. My best regards to you all, and wishes for a very happy new year! (George also has a new page on Pentomino Pair Oddities)
Order-6 Configuration: At 96_6 Configuration, a discovery of L. W. Berman.

Angle Numbers: Each number has that many angles.

12 Octagon Toroid: It's possible to make a toroid with 12 octagons. By Ivan Neretin. Part of Minimal surfaces for planar octagons and nonagons.

Error-correcting Codes: I like the free book Error-Correction Coding and Decoding. Many of the SpringerOpen books are free.
Canonical Tetragonal Antiwedge Hexahedron: The weirdest of the seven hexahedra, the tetragonal antiwedge, is a self-dual polyhedron that has a volume of 3.141 in its canonical form.

Four-Chromatic, No 4-cycles: Part of 4-chromatic unit distance graph with no 4-cycles.

Orchard Problem: As a part of Cultivating New Solutions for the Orchard-Planting Problem, I found a new sporadic solution:

Space-filling Polyhedra: I'd love to see lots of polyhedra based on On Space Groups and Dirichlet-Voronoi Stereohedra.
Fractal Cow-Nautilus: One of the possibilities of the Narayana Cow Triangle Fractal.

A4 Paper Dissection: I found this dissection of an area 200 A4 rectangle into smaller A4 rectangles. Rectangle dissection into similar rectangles. Related is the Delian Brick. I also have this long list of A4 Dissections from Patrick Hamlyn.

Ghee Beom Kim: I really like the math art of Ghee Beom Kim.

Material added 1 Jan 2020

I'm in Art of Computer Programming: A snapshot from Art of Computer Programming, Volume 4. (Pegg). Here's Knuth's Christmas Lecture.

Shattering the Plane: I've found a lot of new simple substitution tilings. These are also available as demo, Substitution Tilings. And a long image list of tilings. Related are Power Clique polyhedra, Wheels of Powered Triangles, and Mersenne Twister and Friends.

Sparse Rulers: I solved the upper bound problem for Sparse Rulers. Soon to be a blog article and proof. I also have a few demos: Sparse Rulers and Wichmann-like Rulers. I wrote Excess01Ruler that can make a sparse ruler for any length. The key to solving the problem is what NJA Sloane called "Dark Satanic Mills on a Cloudy Day". Also, there is my new demo Wichmann Columns.

Venn Illusion: Akiyoshi Kitaoka and Ed Pegg Jr. Based on Venn-5.
The left black circle appears to be smaller than the right one, though they are the same size. Probably won't be an Illusion of the Year.

Unit Distance Graphs: In Dec 2017 I posted Moser Spindles, Golomb Graphs and Root 33. Aubrey de Grey really liked it and had some ideas for improvements. He then managed to solve the Hadwiger–Nelson problem. The latest 5-color graph is down to 510 points.
Tetrahedra and Other Polyhedra: Solid and Dihedral Angles of a Tetrahedron, Canonical Polyhedra, Similarohedrons, and the Tetartoid. The last program was used to make skew dice.
Mondrian Art Problem: Mondrian Art Problem, I solved it with Blanche dissections. My solutions ended up on Numberphile. I found weird bounds in Mondrian Art Problem Upper Bound for defect. I also found Possible Counterexamples to the Minimal Squaring Conjecture. Ponting Square Packing.

Sum of Three Cubes: 569936821221962380720³ + (-569936821113563493509)³ + (-472715493453327032)³ = 3
Crossing Numbers 10&11: There are no Cubic Graphs on 26 Vertices with Crossing Number 10 or 11.
Incredible Rep-Tile: Dmitry Mekhontsev‎ (IFSTile.com) found this order 8 3D rep-tile. He has a whole page of rep-8 tilings.

Graceful Graphs: The Shrikhande Graph is graceful. And so is the toroidial graph next to it. PUZZLE: Fill in the blank squares with 4 integer values from 2 to 21 so that the 22 queen move differences are the values 1 to 22. Hint to make this solvable by logic: Two of the other numbers are 17 and 21. I also made more sextic toroidal graphs.

OEIS: Neil Sloane article at Quanta. And entry A326499 is mine. Also A307450.
Rolling Polyhedra Graphs: I've figured out a lot of Rolling Polyhedra Graphs, including all of the deltahedra. I haven't figured out a good embedding for the dodecahedron. I also like various new mirrored polyhedron sculptures. (and more mirrors) I also found some weird-rolling tetrahedra.

Cut the Knot: Alexander Bogomolny has died. Working with the family, I've been updating Cut-the-Knot and keeping the site alive.
Wang Loops: I like this puzzle by Aaron Wang.

New Coverings Found: L's in Circles, Triangles in Circles, and Circles carrying Circles.

Configurations: I wondered if there was a configuration of barycentric points and lines where the points and lines were the same. I found a lot of 24_3 solutions and a 27_4 solution.

Facebook Puzzle Fun: From the Puzzle Fun page. Patrick Mark Hamlyn‎: The 196 one-sided heptominoes arranged into 28 congruent shapes of 7 pieces each, 3-colored.
Difference Set: The {0,3,4,9,11}_21 difference set in circles and lines. All points 0-20 are connected by a circle or line. Can anyone do the {0,1,3,8,12,18}_31 (0-30) difference set?

Me: I'm doing okay. Here's a picture of me in my office at my latest birthday. Most of my recent work has been at Wolfram Community, Wolfram Demonstrations, Facebook, or StackExchange. Looks like I'm 6 years behind. So much more material to post.
: And one of me at the Periodic Table Table

Puzzlium: Puzzlium has worked with a lot of people recently. One by me from their Puzzle Box series: Arrange the numbers 1 to 9 in the boxes below so that each line of three boxes sums to 14. Three numbers have already been placed.

Highway Interchange: I liked this Highway Interchange.
Robert Abbott: Robert Abbott has passed away, leaving behind some great games and mazes like Where Are the Cows? For Elwyn Berlekamp, I rather like the Triangle game.
Black Holes: Neutron Star Map. Center of the Galaxy. Black Hole Visualization.

Material added 1 Jan 2019

Print 3D Puzzles: Some discussion of Oskar van Deventer and George Miller is in the article The Puzzle Masters.
Ever See A Tree in a Movie?: Trees for movies are being outsourced to SpeedTree now.
Martin Gardner -- The Best Friend Mathematics Ever Had: Colm Mulcahy wrote a blog article on Martin Gardner.
Snake Polyominoes: Shade 16 squares in a 5x10 rectangle so that the remaining square make an obvious path. The resulting snake polyomino is unique.
New Morpion bound: Morpion Solitaire 5D: a new upper bound of 121 on the maximum score.
Ruben's Tube: Sound, fire, and sine waves are shown in a Ruben's Tube (youtube).
Loss of a Mail Service: For fifteen years, I had a system for doing updates involving mail sorting and sending messages to tabs. Sometimes dozens of tabs as I boiled down an update. Unfortunately, Yahoo decided to kill the mail service I was used to, and it's taken me a long time to recover. Part of the process was keeping up with the mail, which I find harder to do in the "new and improved" systems. I'll agree that they look better.
Party Like it's 19999999...: 2 10^1059002 -1, or 19999999999999...9999, is prime. It's the first near-repdigit prime found with over a million digits. Found by Serge Batalov.
Impossible Fractal Sphere: I liked this impossible fractal sphere .
Attacking a Triangle: For an order 20 triangle, 9 vertices can be selected that attack all other vertices.
All the colors: At allRGB, interesting math produces 4096x4096 images where every pixel is a different color.
Doyle Spiral: The Doyle spiral circle packing is quite beautiful.
Lines through the United States: Connect two points of the same US state with a straight line. What's the most other states the line can pass through? Lines through States has the answer.
Prisoners Dilemma: Prisoners do better with Prisoner's Dilemma than normal students.
New Puzzles: The 2013 Nob Yoshigahara Puzzle Design Competition has the 2013 entries and winners.
Seven Consecutive Consonants: A "backlit LCD screen" has 7 consonants in a row. Find some other items with this property.
1. A well-known phrase.
2. A well-known movie.
3. A 2nd grade math topic.
4. A beverage.
5. A piano tune.

Material added 7-11

Puzzle Solving Cockatoos: Cockatoos are rather good at solving parrot-friendly puzzles.
Number Maze: joedev made a great series of number mazes.
Advance in Elliptic Curve Theory: There are advances on the Minimalist Conjecture.
Ancient Greek Geometry Challenges: These geometry challenges are quite well done, all with an HTML5 interface.
ANAGRAMATRON: Bruce Oberg pointed me to Anagramatron, which scrapes Twitter and looks for anagrams.
I should not be awake right now = I wonder who she is talking to.
"Holy crap I'm late" ~ "metaphorically"
Absolutely apathetic = Especially about that.
2¹⁰⁶¹-1 Factored Last Year: The Cunningham Project factored 2¹⁰⁶¹-1 last year.
Crawling Metal Polyhedron: I liked this slow-moving walking metal polyhedron.
Ghost Diagrams: At Ghost Diagrams, shapes with rules try to fit together.
Paul Nylander's Math Artwork: I'm not sure if I've linked to Paul Nylander's Math Artwork site, yet.
Proofs with Problems: I liked the wikipedia Proofs with Problems, and also the mathoverflow discussion.
Covering the Alphabet: Queen Alexandra of Yugoslavia and Herbert Norman Schwarzkopf, Jr. are two names in Wikipedia that cover the alphabet. Is there a shorter pair of names with the same property?

Site Goals

Martin Gardner celebrates math puzzles and Mathematical Recreations. This site aims to do the same. If you've made a good, new math puzzle, send it to ed@mathpuzzle.com. My mail address is Ed Pegg Jr, 1607 Park Haven, Champaign, IL 61820. You can join my moderated recreational mathematics email list at http://groups.yahoo.com/group/mathpuzzle/. My facebook page is at Ed Pegg Jr.

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