n | a(n) |
---|---|
0 | 1 |
1 | 0 |
2 | 4 |
3 | 18 |
4 | 48 |
5 | 1320 |
6 | 4200 |
7 | 115920 |
8 | 994560 |
9 | 11793600 |
10 | 264055680 |
11 | 2601244800 |
12 | 67761429120 |
13 | 1067726499840 |
14 | 21513457405440 |
15 | 485310649824000 |
16 | 9925206939648000 |
17 | 254012624170905600 |
18 | 6174538264806912000 |
19 | 160933619800835481600 |
20 | 4458470291543671603200 |
[1,0,4,18,48,1320,4200,115920,994560,11793600, 264055680,2601244800,67761429120,1067726499840, 21513457405440,485310649824000,9925206939648000, 254012624170905600,6174538264806912000, 160933619800835481600,4458470291543671603200] |