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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 15 |
| 5 | 67 |
| 6 | 457 |
| 7 | 9204 |
| 8 | 586844 |
| 9 | 36708187 |
| 10 | 1582675968 |
| 11 | 49970797654 |
| 12 | 1250823466190 |
[1,2,5,15,67,457,9204,586844,36708187,1582675968, 49970797654,1250823466190] |