MathPuzzle.com (original) (raw)

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.

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, Mn - 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

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

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.