# A162968 (b-file synthesized from sequence entry)
2 1
3 6
4 42
5 312
6 2520
7 22320
8 216720
9 2298240
10 26490240
11 330220800
12 4430764800
13 63707212800
14 977642265600
15 15953627289600
16 275919291648000
17 5042392363008000
18 97102667870208000
19 1965528727658496000
20 41724269440229376000
21 926935665115299840000