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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 6 |
| 2 | 90 |
| 3 | 47250 |
| 4 | 66852843750 |
| 5 | 2806877704512541816406250 |
| 6 | 1216935896582703898519354781702537118597533386230468750 |
[2,6,90,47250,66852843750, 2806877704512541816406250, 12169358965827038985193547817025371185975333862304\ 68750] |