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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 2 |
| 6 | 5 |
| 7 | 4 |
| 8 | 17 |
| 9 | 22 |
| 10 | 165 |
| 11 | 538 |
| 12 | 18972 |
| 13 | 389426 |
| 14 | 50314715 |
[1,0,1,2,2,5,4,17,22,165,538,18972,389426, 50314715] |