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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 60 |
| 5 | 694 |
| 6 | 10790 |
| 7 | 210124 |
| 8 | 4963734 |
| 9 | 139478544 |
| 10 | 4585556242 |
| 11 | 173882670804 |
[1,2,8,60,694,10790,210124,4963734,139478544, 4585556242,173882670804] |