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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 15 |
| 3 | 89 |
| 4 | 547 |
| 5 | 3381 |
| 6 | 20911 |
| 7 | 129329 |
| 8 | 799835 |
| 9 | 4946509 |
| 10 | 30591143 |
| 11 | 189187465 |
| 12 | 1170008467 |
| 13 | 7235785189 |
| 14 | 44748896799 |
| 15 | 276744502881 |
| 16 | 1711495152971 |
| 17 | 10584548667901 |
| 18 | 65458946997783 |
| 19 | 404823472069561 |
| 20 | 2503585087356803 |
[3,15,89,547,3381,20911,129329,799835,4946509, 30591143,189187465,1170008467,7235785189, 44748896799,276744502881,1711495152971, 10584548667901,65458946997783,404823472069561, 2503585087356803] |