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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 7 |
| 4 | 9 |
| 5 | 21 |
| 6 | 31 |
| 7 | 63 |
| 8 | 751 |
| 9 | 1743 |
| 10 | 2205 |
| 11 | 12345 |
| 12 | 16689 |
| 13 | 20111 |
| 14 | 26607 |
| 15 | 32247 |
| 16 | 119595 |
| 17 | 437829 |
| 18 | 2834567 |
[1,3,7,9,21,31,63,751,1743,2205,12345,16689,20111, 26607,32247,119595,437829,2834567] |