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| n | a(n) |
|---|---|
| 1 | 15 |
| 2 | 159 |
| 3 | 973 |
| 4 | 6477 |
| 5 | 46713 |
| 6 | 334521 |
| 7 | 2375879 |
| 8 | 16872055 |
| 9 | 119936863 |
| 10 | 852644471 |
| 11 | 6060859773 |
| 12 | 43081768317 |
| 13 | 306237423553 |
| 14 | 2176828198993 |
| 15 | 15473532443783 |
| 16 | 109990357259447 |
| 17 | 781843471181927 |
| 18 | 5557571249357231 |
| 19 | 39504835607986701 |
[15,159,973,6477,46713,334521,2375879,16872055, 119936863,852644471,6060859773,43081768317, 306237423553,2176828198993,15473532443783, 109990357259447,781843471181927,5557571249357231, 39504835607986701] |