# A110561 (b-file synthesized from sequence entry)
0 1
1 1
2 1
3 3
4 8
5 40
6 180
7 140
8 896
9 72576
10 604800
11 6652800
12 68428800
13 59304960
14 726485760
15 163459296000
16 2324754432000
17 39520825344000
18 640237370572800
19 579262382899200
20 10532043325440000
21 4644631106519040000