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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 222 |
| 5 | 2428912878 |
| 6 | 84539502447168140812774402430429967456348471246 |
[1,2,6,222,2428912878, 84539502447168140812774402430429967456348471246] |