n | a(n) |
---|---|
1 | 1 |
2 | 1 |
3 | 0 |
4 | 4 |
5 | 20 |
6 | 144 |
7 | 630 |
8 | 5696 |
9 | 39366 |
10 | 366400 |
11 | 3634950 |
12 | 39066624 |
13 | 479163828 |
14 | 6226534272 |
15 | 87238701000 |
16 | 1315130458112 |
17 | 20922813624336 |
18 | 355586138666496 |
19 | 6402373841107998 |
20 | 121479626301440000 |
[1,1,0,4,20,144,630,5696,39366,366400,3634950, 39066624,479163828,6226534272,87238701000, 1315130458112,20922813624336,355586138666496, 6402373841107998,121479626301440000] |