The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 70 |
| 4 | 6516 |
| 5 | 1741480 |
| 6 | 1297416720 |
| 7 | 2686765690144 |
| 8 | 15449867954722880 |
[1,3,70,6516,1741480,1297416720,2686765690144, 15449867954722880] |