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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 69 |
| 5 | 811 |
| 6 | 23372 |
| 7 | 1073376 |
| 8 | 67963017 |
| 9 | 5492554668 |
| 10 | 548974274040 |
[1,3,10,69,811,23372,1073376,67963017,5492554668, 548974274040] |