The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 392 |
| 7 | 1810 |
| 8 | 10400 |
| 9 | 72228 |
| 10 | 589674 |
| 11 | 3823906 |
| 12 | 29420944 |
| 13 | 266232984 |
| 14 | 2711139976 |
| 15 | 30669073348 |
| 16 | 316482938974 |
[1,2,6,24,120,392,1810,10400,72228,589674,3823906, 29420944,266232984,2711139976,30669073348, 316482938974] |