# A002435 (b-file synthesized from sequence entry) 1 0 2 2 3 6 4 28 5 180 6 662 7 7266 8 24568 9 408360 10 1326122 11 30974526 12 98329108 13 3065784540 14 9596075582 15 384653685786 16 1192744081648 17 59724464976720 18 183983154281042 19 11249503075325046 20 34489251602450188