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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 144 |
| 6 | 720 |
| 7 | 518400 |
| 8 | 54432000 |
| 9 | 121927680000 |
| 10 | 23044331520000 |
| 11 | 83623270219776000000 |
| 12 | 32194959034613760000000 |
| 13 | 15421436889514446422016000000000 |
| 14 | 297710839152076388177018880000000000 |
| 15 | 267015660792140704250415525396480000000000 |
[1,1,2,6,144,720,518400,54432000,121927680000, 23044331520000,83623270219776000000, 32194959034613760000000, 15421436889514446422016000000000, 297710839152076388177018880000000000, 267015660792140704250415525396480000000000] |