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| n | a(n) |
|---|---|
| 2 | 4 |
| 3 | 108 |
| 4 | 3456 |
| 5 | 3600000 |
| 6 | 48600000 |
| 7 | 8004837960000 |
| 8 | 43717088378880000 |
| 9 | 3319007595022909440000 |
| 10 | 2592974683611648000000000 |
| 11 | 82200659870363161557652992000000000 |
| 12 | 98640791844435793869183590400000000 |
| 13 | 2715985485838884679142342027478742851379200000000 |
[4,108,3456,3600000,48600000,8004837960000, 43717088378880000,3319007595022909440000, 2592974683611648000000000, 82200659870363161557652992000000000, 98640791844435793869183590400000000, 2715985485838884679142342027478742851379200000000] |