# A001335 (b-file synthesized from sequence entry) 0 1 1 0 2 0 3 12 4 24 5 60 6 180 7 588 8 1968 9 6840 10 24240 11 87252 12 318360 13 1173744 14 4366740 15 16370700 16 61780320 17 234505140 18 894692736 19 3429028116 20 13195862760 21 50968206912 22 197517813636 23 767766750564 24 2992650987408 25 11694675166500 26 45807740881032