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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 20 |
| 3 | 860 |
| 4 | 57200 |
| 5 | 5344800 |
| 6 | 682612800 |
| 7 | 118180104000 |
| 8 | 27396820448000 |
| 9 | 8312583863720000 |
| 10 | 3209035788149600000 |
| 11 | 1534218535286625760000 |
| 12 | 888028389273314675200000 |
| 13 | 611029957551257895664000000 |
| 14 | 492466785518772137553984000000 |
| 15 | 459270692175324078697443840000000 |
[1,1,20,860,57200,5344800,682612800,118180104000, 27396820448000,8312583863720000, 3209035788149600000,1534218535286625760000, 888028389273314675200000, 611029957551257895664000000, 492466785518772137553984000000, 459270692175324078697443840000000] |