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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 24 |
| 5 | 144 |
| 6 | 960 |
| 7 | 5760 |
| 8 | 40320 |
| 9 | 524160 |
| 10 | 4354560 |
| 11 | 43545600 |
| 12 | 638668800 |
| 13 | 6706022400 |
| 14 | 99632332800 |
| 15 | 2092278988800 |
| 16 | 20922789888000 |
| 17 | 376610217984000 |
| 18 | 9247873130496000 |
| 19 | 128047474114560000 |
| 20 | 2919482409811968000 |
| 21 | 77852864261652480000 |
[1,2,8,24,144,960,5760,40320,524160,4354560, 43545600,638668800,6706022400,99632332800, 2092278988800,20922789888000,376610217984000, 9247873130496000,128047474114560000, 2919482409811968000,77852864261652480000] |