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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 9 |
| 3 | 21 |
| 4 | 115 |
| 5 | 521 |
| 6 | 1494 |
| 7 | 15129 |
| 8 | 83609 |
| 9 | 459957 |
| 10 | 2551794 |
| 11 | 14150081 |
| 12 | 78597739 |
[1,1,9,21,115,521,1494,15129,83609,459957,2551794, 14150081,78597739] |