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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 18 |
| 5 | 85 |
| 6 | 657 |
| 7 | 4374 |
| 8 | 55711 |
| 9 | 530502 |
| 10 | 6603007 |
| 11 | 82736601 |
| 12 | 2032940127 |
| 13 | 32102236563 |
[1,1,1,3,18,85,657,4374,55711,530502,6603007, 82736601,2032940127,32102236563] |