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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 15 |
| 5 | 51 |
| 6 | 194 |
| 7 | 810 |
| 8 | 3675 |
| 9 | 17935 |
| 10 | 93481 |
| 11 | 517129 |
| 12 | 3021133 |
[1,1,2,5,15,51,194,810,3675,17935,93481,517129, 3021133] |