# A012912 (b-file synthesized from sequence entry) 0 1 1 2 2 4 3 8 4 16 5 42 6 184 7 1192 8 8320 9 63954 10 529824 11 5076392 12 52633728 13 615675322 14 7595502464 15 104080146632 16 1487529832448 17 23400806440098 18 380497987834368 19 6758267272643528 20 123182327672588288