The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 66 |
| 5 | 4200 |
| 6 | 4192200 |
| 7 | 5115600 |
| 8 | 19083776176080 |
| 9 | 10086416728304192640 |
| 10 | 126556188275836361347200 |
| 11 | 451535899566923284351392000 |
| 12 | 1253032399528279799996000622278320876800 |
[1,1,6,66,4200,4192200,5115600,19083776176080, 10086416728304192640,126556188275836361347200, 451535899566923284351392000, 1253032399528279799996000622278320876800] |