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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 40320 |
| 9 | 3265920 |
| 10 | 81648000 |
| 11 | 1097712000 |
| 12 | 9879408000 |
| 13 | 66784798080 |
| 14 | 363606122880 |
| 15 | 1669619952000 |
| 16 | 6678479808000 |
| 17 | 23828156352000 |
| 18 | 77203226580480 |
| 19 | 230333593351680 |
| 20 | 639815537088000 |
| 21 | 1669577821632000 |
| 22 | 4122835028928000 |
[0,0,0,0,0,0,0,40320,3265920,81648000,1097712000, 9879408000,66784798080,363606122880,1669619952000, 6678479808000,23828156352000,77203226580480, 230333593351680,639815537088000,1669577821632000, 4122835028928000] |