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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 17 |
| 5 | 53 |
| 6 | 273 |
| 7 | 3001 |
| 8 | 57769 |
| 9 | 1501233 |
| 10 | 44477633 |
| 11 | 2219720427 |
| 12 | 183391587053 |
| 13 | 21595528376763 |
[1,1,1,17,53,273,3001,57769,1501233,44477633, 2219720427,183391587053,21595528376763] |