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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 15 |
| 3 | 97 |
| 4 | 587 |
| 5 | 3615 |
| 6 | 22387 |
| 7 | 138505 |
| 8 | 856719 |
| 9 | 5299373 |
| 10 | 32780447 |
| 11 | 202770557 |
| 12 | 1254280765 |
| 13 | 7758622663 |
| 14 | 47992624925 |
| 15 | 296868677731 |
| 16 | 1836344895365 |
| 17 | 11359105312193 |
| 18 | 70264182844421 |
| 19 | 434634177177689 |
| 20 | 2688522947592119 |
[1,15,97,587,3615,22387,138505,856719,5299373, 32780447,202770557,1254280765,7758622663, 47992624925,296868677731,1836344895365, 11359105312193,70264182844421,434634177177689, 2688522947592119] |