The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 4908 |
| 8 | 38208 |
| 9 | 334368 |
| 10 | 3248640 |
| 11 | 34774112 |
| 12 | 405758208 |
| 13 | 5129918808 |
| 14 | 69849531936 |
| 15 | 1018876044528 |
| 16 | 15854497560576 |
| 17 | 262116761475488 |
| 18 | 4588408779868800 |
| 19 | 84784281517177940 |
| 20 | 1649073291620014880 |
| 21 | 33678805727832427224 |
| 22 | 720569710852319474016 |
[1,1,2,6,24,120,720,4908,38208,334368,3248640, 34774112,405758208,5129918808,69849531936, 1018876044528,15854497560576,262116761475488, 4588408779868800,84784281517177940, 1649073291620014880,33678805727832427224, 720569710852319474016] |