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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 15 |
| 3 | 63 |
| 4 | 251 |
| 5 | 1001 |
| 6 | 4001 |
| 7 | 16001 |
| 8 | 63985 |
| 9 | 255867 |
| 10 | 1023171 |
| 11 | 4091495 |
| 12 | 16361227 |
| 13 | 65425905 |
| 14 | 261627633 |
| 15 | 1046206665 |
| 16 | 4183611549 |
| 17 | 16729587163 |
| 18 | 66898918163 |
| 19 | 267517973263 |
| 20 | 1069761185739 |
| 21 | 4277802274577 |
| 22 | 17106240667845 |
| 23 | 68405094720089 |
[3,15,63,251,1001,4001,16001,63985,255867,1023171, 4091495,16361227,65425905,261627633,1046206665, 4183611549,16729587163,66898918163,267517973263, 1069761185739,4277802274577,17106240667845, 68405094720089] |