# A022491 (b-file synthesized from sequence entry)
1 0
2 1
3 2
4 6
5 18
6 72
7 321
8 1680
9 9852
10 64168
11 457659
12 3543785
13 29578097
14 264623046
15 2525897073
16 25622275565
17 275257714175
18 3122190896616
19 37290114445901
20 467812869356846