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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 26 |
| 6 | 117 |
| 7 | 6851 |
| 8 | 85249444 |
| 9 | 39565495603665 |
| 10 | 40261075301026166295207 |
[0,0,1,3,7,26,117,6851,85249444,39565495603665, 40261075301026166295207] |