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| n | a(n) |
|---|---|
| 2 | 2 |
| 3 | 6 |
| 4 | 60 |
| 5 | 2914 |
| 6 | 1216320 |
| 7 | 1982323016 |
| 8 | 10802428568204 |
| 9 | 144294430454318540 |
[2,6,60,2914,1216320,1982323016,10802428568204, 144294430454318540] |