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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 18 |
| 5 | 59 |
| 6 | 306 |
| 7 | 1861 |
| 8 | 15097 |
| 9 | 146893 |
| 10 | 1693416 |
| 11 | 22239872 |
| 12 | 327670703 |
[1,2,5,18,59,306,1861,15097,146893,1693416, 22239872,327670703] |