# A255506 (b-file synthesized from sequence entry)
0 2
1 12
2 120
3 504
4 1440
5 3168
6 3931200
7 8640
8 41126400
9 579156480
10 2395008000
11 1001548800
12 2615348736000
13 5748019200
14 21670032384000
15 7491404919398400
16 21341245685760000
17 251073478656000
18 24574743184592240640000
19 76828484468736000
20 65834328341259878400000