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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 9 |
| 3 | 110 |
| 4 | 2116 |
| 5 | 59670 |
| 6 | 2509056 |
| 7 | 147357840 |
| 8 | 12001640704 |
| 9 | 1321710590682 |
| 10 | 196996776086916 |
[2,9,110,2116,59670,2509056,147357840,12001640704, 1321710590682,196996776086916] |