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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 77 |
| 5 | 1069 |
| 6 | 13041 |
| 7 | 153389 |
| 8 | 1691609 |
| 9 | 18175623 |
| 10 | 192338138 |
[0,1,1,6,77,1069,13041,153389,1691609,18175623, 192338138] |