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 | 119 |
| 6 | 708 |
| 7 | 4914 |
| 8 | 38976 |
| 9 | 347775 |
| 10 | 3447912 |
| 11 | 37601586 |
| 12 | 447346944 |
| 13 | 5765604885 |
| 14 | 80025786960 |
| 15 | 1190085736014 |
| 16 | 18877969022976 |
| 17 | 318171464604945 |
| 18 | 5677939605422880 |
| 19 | 106955077375109430 |
| 20 | 2120744934976978944 |
| 21 | 44153462828412744975 |
| 22 | 963040357207773472320 |
[1,2,6,24,119,708,4914,38976,347775,3447912, 37601586,447346944,5765604885,80025786960, 1190085736014,18877969022976,318171464604945, 5677939605422880,106955077375109430, 2120744934976978944,44153462828412744975, 963040357207773472320] |