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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 144 |
| 5 | 1440 |
| 6 | 7200 |
| 7 | 25200 |
| 8 | 141120 |
| 9 | 2032128 |
| 10 | 52254720 |
| 11 | 1026432000 |
| 12 | 9408960000 |
| 13 | 57081024000 |
| 14 | 528881633280 |
| 15 | 12116197416960 |
| 16 | 479322095616000 |
| 17 | 14071151001600000 |
| 18 | 187950374092800000 |
| 19 | 1624830984032256000 |
| 20 | 21032437860687052800 |
| 21 | 661340826849411072000 |
[1,1,2,12,144,1440,7200,25200,141120,2032128, 52254720,1026432000,9408960000,57081024000, 528881633280,12116197416960,479322095616000, 14071151001600000,187950374092800000, 1624830984032256000,21032437860687052800, 661340826849411072000] |