The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 24 |
| 4 | 40 |
| 5 | 180 |
| 6 | 440 |
| 7 | 3640 |
| 8 | 18480 |
| 9 | 137280 |
| 10 | 1320 |
| 11 | 703560 |
| 12 | 15960 |
| 13 | 1256640 |
| 14 | 1436160 |
| 15 | 96360 |
[1,6,24,40,180,440,3640,18480,137280,1320,703560, 15960,1256640,1436160,96360] |