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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 100 |
| 5 | 794 |
| 6 | 11268 |
| 7 | 264083 |
| 8 | 11030649 |
| 9 | 813916625 |
| 10 | 107746920222 |
| 11 | 24945674297719 |
| 12 | 9651792274718292 |
[2,6,18,100,794,11268,264083,11030649,813916625, 107746920222,24945674297719,9651792274718292] |