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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 13 |
| 3 | 93 |
| 4 | 635 |
| 5 | 4357 |
| 6 | 27989 |
| 7 | 175599 |
| 8 | 1097149 |
| 9 | 6898767 |
| 10 | 43661399 |
| 11 | 277088463 |
| 12 | 1758632349 |
| 13 | 11151301399 |
| 14 | 70656266965 |
| 15 | 447562532731 |
| 16 | 2835123056355 |
| 17 | 17961560639715 |
| 18 | 113803029648973 |
| 19 | 721065928522417 |
| 20 | 4568695947257233 |
[2,13,93,635,4357,27989,175599,1097149,6898767, 43661399,277088463,1758632349,11151301399, 70656266965,447562532731,2835123056355, 17961560639715,113803029648973,721065928522417, 4568695947257233] |