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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 9 |
| 4 | 56 |
| 5 | 499 |
| 6 | 8000 |
| 7 | 207554 |
| 8 | 9382078 |
| 9 | 723818669 |
| 10 | 93919689474 |
| 11 | 19191447316594 |
| 12 | 5833792312541241 |
[2,4,9,56,499,8000,207554,9382078,723818669, 93919689474,19191447316594,5833792312541241] |