The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 144 |
| 6 | 1008 |
| 7 | 8064 |
| 8 | 72576 |
| 9 | 766080 |
| 10 | 8934912 |
| 11 | 113895936 |
| 12 | 1573254144 |
| 13 | 23864924160 |
| 14 | 389247344640 |
| 15 | 6786673496064 |
| 16 | 125855767166976 |
| 17 | 2492616008171520 |
| 18 | 52243870155079680 |
| 19 | 1154797100239749120 |
| 20 | 26835102086208159744 |
| 21 | 656159502089355264000 |
[1,1,2,6,24,144,1008,8064,72576,766080,8934912, 113895936,1573254144,23864924160,389247344640, 6786673496064,125855767166976,2492616008171520, 52243870155079680,1154797100239749120, 26835102086208159744,656159502089355264000] |