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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 1440 |
| 5 | 7257600 |
| 6 | 4981616640000 |
| 7 | 1190690865178214400000 |
| 8 | 272795714695463271824306995200000 |
| 9 | 157357907118293002525216789633250308915200000000 |
[1,2,12,1440,7257600,4981616640000, 1190690865178214400000, 272795714695463271824306995200000, 157357907118293002525216789633250308915200000000] |