The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 3 |
| 2 | 15 |
| 3 | 780 |
| 4 | 3828 |
| 5 | 198135 |
| 6 | 972315 |
| 7 | 50325528 |
| 8 | 246964200 |
| 9 | 12782485995 |
| 10 | 62727934503 |
| 11 | 3246701117220 |
| 12 | 15932648399580 |
| 13 | 824649301287903 |
| 14 | 4046829965558835 |
| 15 | 209457675826010160 |
| 16 | 1027878878603544528 |
| 17 | 53201425010505292755 |
| 18 | 261077188335334751295 |
| 19 | 13512952494992518349628 |
[0,3,15,780,3828,198135,972315,50325528,246964200, 12782485995,62727934503,3246701117220, 15932648399580,824649301287903,4046829965558835, 209457675826010160,1027878878603544528, 53201425010505292755,261077188335334751295, 13512952494992518349628] |