n | a(n) |
---|---|
0 | 1 |
1 | 1 |
2 | 4 |
3 | 15 |
4 | 104 |
5 | 750 |
6 | 7254 |
7 | 74214 |
8 | 914528 |
9 | 12202632 |
10 | 183781080 |
11 | 2974435200 |
12 | 52965004872 |
13 | 1006137926040 |
14 | 20652503811744 |
15 | 449786292039000 |
16 | 10452618371303040 |
17 | 256326394027746240 |
18 | 6648055804021356864 |
19 | 181094856954089764032 |
20 | 5184169133931737988480 |
[1,1,4,15,104,750,7254,74214,914528,12202632, 183781080,2974435200,52965004872,1006137926040, 20652503811744,449786292039000,10452618371303040, 256326394027746240,6648055804021356864, 181094856954089764032,5184169133931737988480] |