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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 14 |
| 4 | 58 |
| 5 | 293 |
| 6 | 1761 |
| 7 | 12331 |
| 8 | 98650 |
| 9 | 887855 |
| 10 | 8878555 |
| 11 | 97664108 |
| 12 | 1171969305 |
| 13 | 15235600969 |
| 14 | 213298413570 |
| 15 | 3199476203552 |
| 16 | 51191619256832 |
| 17 | 870257527366148 |
| 18 | 15664635492590668 |
| 19 | 297628074359222695 |
| 20 | 5952561487184453911 |
[2,4,14,58,293,1761,12331,98650,887855,8878555, 97664108,1171969305,15235600969,213298413570, 3199476203552,51191619256832,870257527366148, 15664635492590668,297628074359222695, 5952561487184453911] |