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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 17 |
| 5 | 57 |
| 6 | 337 |
| 7 | 4357 |
| 8 | 135183 |
| 9 | 3521533 |
| 10 | 135176521 |
| 11 | 9933992919 |
| 12 | 1311405922839 |
[1,1,1,17,57,337,4357,135183,3521533,135176521, 9933992919,1311405922839] |