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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 9 |
| 6 | 30 |
| 7 | 89 |
| 8 | 379 |
| 9 | 1864 |
| 10 | 12365 |
| 11 | 106951 |
| 12 | 1272286 |
| 13 | 20722347 |
[1,1,2,4,9,30,89,379,1864,12365,106951,1272286, 20722347] |