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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 120 |
| 3 | 20880 |
| 4 | 7244160 |
| 5 | 4193683200 |
| 6 | 3648171985920 |
| 7 | 4450790792448000 |
| 8 | 7251098441261875200 |
| 9 | 15208619045076276019200 |
| 10 | 39919072914444753469440000 |
| 11 | 128188338317208930555828633600 |
| 12 | 494389344738688341547326898176000 |
| 13 | 2255096937522349816552823932846080000 |
[1,2,120,20880,7244160,4193683200,3648171985920, 4450790792448000,7251098441261875200, 15208619045076276019200, 39919072914444753469440000, 128188338317208930555828633600, 494389344738688341547326898176000, 2255096937522349816552823932846080000] |