n | a(n) |
---|---|
1 | 1 |
2 | 4 |
3 | 20 |
4 | 110 |
5 | 640 |
6 | 3870 |
7 | 24084 |
8 | 153306 |
9 | 993978 |
10 | 6544242 |
11 | 43652340 |
12 | 294469974 |
13 | 2006018748 |
14 | 13784115468 |
15 | 95444016984 |
16 | 665407010349 |
17 | 4667570034444 |
18 | 32922870719664 |
19 | 233389493503968 |
20 | 1662048903052380 |
21 | 11885333877149532 |
[1,4,20,110,640,3870,24084,153306,993978,6544242, 43652340,294469974,2006018748,13784115468, 95444016984,665407010349,4667570034444, 32922870719664,233389493503968,1662048903052380, 11885333877149532] |