The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 8 |
| 3 | 72 |
| 4 | 576 |
| 5 | 5120 |
| 6 | 41472 |
| 7 | 364544 |
| 8 | 2949120 |
| 9 | 25952256 |
| 10 | 209977344 |
| 11 | 1830813696 |
| 12 | 14931722240 |
| 13 | 129251672064 |
| 14 | 1053340729344 |
| 15 | 9123584278528 |
| 16 | 74294344286208 |
| 17 | 639503450505216 |
| 18 | 5239722662166528 |
| 19 | 44846880273727488 |
| 20 | 367008185258606592 |
| 21 | 3144110674230116352 |
| 22 | 25718087147075928064 |
[1,1,8,72,576,5120,41472,364544,2949120,25952256, 209977344,1830813696,14931722240,129251672064, 1053340729344,9123584278528,74294344286208, 639503450505216,5239722662166528, 44846880273727488,367008185258606592, 3144110674230116352,25718087147075928064] |