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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 33 |
| 6 | 128 |
| 7 | 564 |
| 8 | 2681 |
| 9 | 13845 |
| 10 | 76661 |
| 11 | 453025 |
| 12 | 2839968 |
| 13 | 18805590 |
[1,1,1,3,9,33,128,564,2681,13845,76661,453025, 2839968,18805590] |