"Every time you shuffle a deck of playing cards, it's likely that you have come up with an ordering of cards that is unique in human history."

legitimate theorem about bodyswitching

"A Fibonacci word is a specific sequence of binary digits (or symbols from any two-letter alphabet). The Fibonacci word is formed by repeated concatenation in the same way that the Fibonacci numbers are formed by repeated addition."

"Here you'll find a fully functional 120 Cell permutation puzzle, which can be considered the 4-dimensional analogue of Megaminx."

"The Megaminx is a dodecahedron-shaped puzzle similar to the Rubik's Cube. It has a total of 50 movable pieces to rearrange, compared to the 20 of the Rubik's cube."

database of hashi bridge-building puzzles

"Hashiwokakero is played on a rectangular grid with no standard size, although the grid itself is not usually drawn. Some cells start out with (usually encircled) numbers from 1 to 8 inclusive; these are the islands. The rest of the cells are empty. The goal is to connect all of the islands into a single connected group by drawing a series of bridges between the islands. The bridges must follow certain criteria."

good thread on string permutation implementations in haskell

"A typical function will, given a sequence of elements such as (1, 1, 2, 2), permute on indices only. This will in our case give 4! permutations, which is often not what we want. The STL implementation will “correctly” generate only unique permutations, in our case 4! / 2!2!, and also generate them in the right order.

What’s special about most STL implementations is the use of a fairly unknown algorithm for finding permutations in lexicographic order. A canonical templated implementation is usually about 25 lines of code. It is also non-recursive and very fast."