# A064595 (b-file synthesized from sequence entry) 1 24 2 112 3 1984 4 2520 5 31320 6 32512 7 1163160 8 2208384 9 3053232 10 6535296 11 13472928 12 123165600 13 134201344 14 186076800 15 365959296 16 3456573120 17 4401782352 18 5517818880 19 18924364800 20 34359476224 21 325377803520