# A097971 (b-file synthesized from sequence entry)
2 2
3 10
4 56
5 360
6 2640
7 21840
8 201600
9 2056320
10 22982400
11 279417600
12 3672345600
13 51891840000
14 784604620800
15 12640852224000
16 216202162176000
17 3912561709056000
18 74694359900160000
19 1500289571708928000
20 31627726106296320000
21 698242876346695680000