n | a(n) |
---|---|
0 | 0 |
1 | 0 |
2 | 2 |
3 | 12 |
4 | 60 |
5 | 320 |
6 | 1950 |
7 | 13692 |
8 | 109592 |
9 | 986400 |
10 | 9864090 |
11 | 108505100 |
12 | 1302061332 |
13 | 16926797472 |
14 | 236975164790 |
15 | 3554627472060 |
16 | 56874039553200 |
17 | 966858672404672 |
18 | 17403456103284402 |
19 | 330665665962403980 |
20 | 6613313319248079980 |
21 | 138879579704209680000 |
[0,0,2,12,60,320,1950,13692,109592,986400,9864090, 108505100,1302061332,16926797472,236975164790, 3554627472060,56874039553200,966858672404672, 17403456103284402,330665665962403980, 6613313319248079980,138879579704209680000] |