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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 21 |
| 3 | 125 |
| 4 | 765 |
| 5 | 4657 |
| 6 | 28373 |
| 7 | 172833 |
| 8 | 1052829 |
| 9 | 6413369 |
| 10 | 39067429 |
| 11 | 237981569 |
| 12 | 1449678893 |
| 13 | 8830805161 |
| 14 | 53793374581 |
| 15 | 327685538769 |
| 16 | 1996115937021 |
| 17 | 12159458878905 |
| 18 | 74070066514885 |
| 19 | 451202212873441 |
| 20 | 2748525099013581 |
[3,21,125,765,4657,28373,172833,1052829,6413369, 39067429,237981569,1449678893,8830805161, 53793374581,327685538769,1996115937021, 12159458878905,74070066514885,451202212873441, 2748525099013581] |