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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 864 |
| 5 | 43200000 |
| 6 | 272097792000000000 |
| 7 | 3416681839784939886182400000000000 |
| 8 | 1847600699255039694224318542233446367734016245760000000000000000 |
[1,1,6,864,43200000,272097792000000000, 3416681839784939886182400000000000, 18476006992550396942243185422334463677340162457600\ 00000000000000] |