# A065953 (b-file synthesized from sequence entry) 0 1 1 1 2 1 3 1 4 1 5 2 6 6 7 8 8 40 9 720 10 560 11 4480 12 362880 13 1209600 14 13305600 15 479001600 16 188697600 17 2641766400 18 1307674368000 19 774918144000 20 1197600768000 21 44771844096000 22 3119105138688000 23 73724303278080000 24 4644631106519040000 25 374666909259202560000 26 8617338912961658880000