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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 40320 |
| 9 | 322560 |
| 10 | 2943360 |
| 11 | 30078720 |
| 12 | 339696000 |
| 13 | 4196666880 |
| 14 | 56255149440 |
| 15 | 812752093440 |
| 16 | 12585067447680 |
| 17 | 207863095910400 |
| 18 | 3646938237505920 |
| 19 | 67723519234210560 |
| 20 | 1326863186062565760 |
| 21 | 27349945952061841920 |
| 22 | 591598086412112035200 |
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