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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 48 |
| 4 | 1680384 |
| 5 | 14807804035657359360 |
| 6 | 141377911697227887117195970316200795630205476957716480 |
[1,1,2,48,1680384,14807804035657359360, 14137791169722788711719597031620079563020547695771\ 6480] |