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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 7 |
| 3 | 28 |
| 4 | 287 |
| 5 | 17975 |
| 6 | 689715 |
| 7 | 104189110 |
| 8 | 37047634987 |
| 9 | 20232260136382 |
[1,7,28,287,17975,689715,104189110,37047634987, 20232260136382] |