Can six "$1\times1\times1$ pyramids" fit inside a $1\times1\times1$ cube?
89501
Equidecomposability of a Cube into 6 Trirectangular Tetrahedra
4500
Brute force method of solving the cube: How many moves would it take?
72213
Can a $N-1$ rectifiable set be partitioned into countably many connected pieces?
26878
Primes between consecutive cubes
153769
Numbers that can be expressed as the sum of two cubes in exactly two different ways
43326
Can every group be represented by a group of matrices?
127988
modeling a world made of cubes
26343
Number of certain (0,1)-matrices, Stanley's Enumerative Combinatorics
124253
Triple integral limits over pyramid
107110
Solving Rubik's cube and other permutation puzzles
52594
Can all circles of radius $1/n$ be packed in a unit disk, excluding the circle of radius $1/1$?
120912
Can two Pythagorean triples have the same product?
103081
Square-tiling a torus
42394
Join a list with {6, 6, 2} dimensions with a list {6, 6} dimensions
96086
Double Factorial: Number of possibilities to partition a set of $2n$ items into $n$ pairs
132068
Write the set $\{1, 6, 11, 16,\ldots\}$ in compact (concise) notation.
87833
Volumes of n-balls: what is so special about n=5?