# A012361 (b-file synthesized from sequence entry)
0 0
1 1
2 2
3 6
4 24
5 160
6 1312
7 13496
8 162624
9 2282880
10 36300032
11 646542336
12 12732724224
13 274854736000
14 6451455453952
15 163604692933376
16 4457345570893824
17 129841475781611520
18 4026939664026755072
19 132480317530158575616
20 4607985167132525543424