The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 111 |
| 5 | 1095 |
| 6 | 13605 |
| 7 | 204225 |
| 8 | 3597825 |
| 9 | 72788625 |
| 10 | 1663323795 |
| 11 | 42373980495 |
| 12 | 1190822561775 |
| 13 | 36596898673335 |
| 14 | 1221033470181525 |
| 15 | 43954996792932225 |
| 16 | 1698138394110583425 |
| 17 | 70082689941923083425 |
| 18 | 3077205709746516423075 |
| 19 | 143235112906380591471375 |
[1,1,3,15,111,1095,13605,204225,3597825,72788625, 1663323795,42373980495,1190822561775, 36596898673335,1221033470181525,43954996792932225, 1698138394110583425,70082689941923083425, 3077205709746516423075,143235112906380591471375] |