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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 13 |
| 6 | 61 |
| 7 | 329 |
| 8 | 2787 |
| 9 | 39701 |
| 10 | 747265 |
| 11 | 18941331 |
| 12 | 668354617 |
| 13 | 33772020165 |
[1,1,1,1,13,61,329,2787,39701,747265,18941331, 668354617,33772020165] |