# A002709 (b-file synthesized from sequence entry)
0 1
1 1
2 1
3 5
4 24
5 133
6 846
7 5661
8 39556
9 286000
10 2123329
11 16112057
12 124512556
13 977227830
14 7772368380
15 62535450861
16 508271324688
17 4168218286276
18 34455941596060
19 286864341314320
20 2403705165816240
21 20258850167232165