A general formula giving the number of distinct ways of folding an m×n rectangular map is not known. A distinct folding is defined as a permutation of N = m×n numbered cells reading from the top down. Lunnon gives values up to n = 28. k | OEIS | k×1, k×2, ... 1 | A000136 | 1, 2, 6, 16, 50, 144, 462, 1392, ... 2 | A001415 | 2, 8, 60, 320, 1980, 10512, ... The number of ways to fold an n×n sheet of maps is given for n = 1, 2, ..., etc. by 1, 8, 1368, 300608, 186086600, ... (Lunnon 1971; OEIS A001418).

stamp folding