The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 140 |
| 5 | 700 |
| 6 | 2520 |
| 7 | 44352 |
| 8 | 2196480 |
| 9 | 47567520 |
| 10 | 634233600 |
| 11 | 51753461760 |
| 12 | 13984935444480 |
| 13 | 1448751906201600 |
| 14 | 82605199597240320 |
| 15 | 32797812715211980800 |
| 16 | 5296846753506734899200 |
| 17 | 483765735240908144640000 |
| 18 | 28985693293514522492928000 |
[1,3,15,140,700,2520,44352,2196480,47567520, 634233600,51753461760,13984935444480, 1448751906201600,82605199597240320, 32797812715211980800,5296846753506734899200, 483765735240908144640000, 28985693293514522492928000] |