The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 9 |
| 5 | 1459 |
| 6 | 13975855106 |
| 7 | 442535332406378982945622818194705 |
[1,1,1,2,9,1459,13975855106, 442535332406378982945622818194705] |