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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 69 |
| 5 | 2155 |
| 6 | 34073 |
| 7 | 876047637 |
| 8 | 97090036327 |
| 9 | 420397381695 |
| 10 | 2125899832395 |
| 11 | 3177544777277 |
| 12 | 34434175473881 |
| 13 | 40845965389135 |
[1,3,15,69,2155,34073,876047637,97090036327, 420397381695,2125899832395,3177544777277, 34434175473881,40845965389135] |