# A121586 (b-file synthesized from sequence entry)
0 1
1 1
2 3
3 13
4 70
5 446
6 3276
7 27252
8 253296
9 2602224
10 29288160
11 358457760
12 4740577920
13 67375532160
14 1024208720640
15 16583626886400
16 284953145702400
17 5178968115148800
18 99268112350310400
19 2001336861359001600
20 42337994134947840000
21 937755916997437440000