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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 61 |
| 4 | 1771 |
| 5 | 187223 |
| 6 | 70038280 |
| 7 | 90111497503 |
| 8 | 397783376192189 |
[1,2,7,61,1771,187223,70038280,90111497503, 397783376192189] |