# A009253 (b-file synthesized from sequence entry)
0 1
1 1
2 1
3 6
4 21
5 112
6 717
7 4592
8 38857
9 318208
10 3158329
11 32169984
12 363525789
13 4399544320
14 56250039237
15 779244812288
16 11210469917713
17 173483433263104
18 2783865475754737
19 47421793222656000
20 840008000833503141