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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 61 |
| 6 | 407 |
| 7 | 3226 |
| 8 | 28335 |
| 9 | 262091 |
| 10 | 2501168 |
| 11 | 24328920 |
| 12 | 239931556 |
[1,1,3,12,61,407,3226,28335,262091,2501168, 24328920,239931556] |