n | a(n) |
---|---|
1 | 0 |
2 | 0 |
3 | 6 |
4 | 6 |
5 | 30 |
6 | 72 |
7 | 252 |
8 | 756 |
9 | 2106 |
10 | 6642 |
11 | 19602 |
12 | 59292 |
13 | 176904 |
14 | 530712 |
15 | 1596510 |
16 | 4780782 |
17 | 14351094 |
18 | 43040160 |
19 | 129146724 |
20 | 387440172 |
21 | 1162202418 |
[0,0,6,6,30,72,252,756,2106,6642,19602,59292, 176904,530712,1596510,4780782,14351094,43040160, 129146724,387440172,1162202418] |