The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 45 |
| 4 | 7794 |
| 5 | 2117424 |
| 6 | 10615237672 |
| 7 | 51666240687220 |
| 8 | 4291633334520814783 |
| 9 | 347033965049827951084160 |
[1,4,45,7794,2117424,10615237672,51666240687220, 4291633334520814783,347033965049827951084160] |