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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 10 |
| 3 | 639 |
| 4 | 5537154119 |
| 5 | 4456255064711219 |
| 6 | 40753506500253984833129731848456 |
[2,10,639,5537154119,4456255064711219, 40753506500253984833129731848456] |