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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 15 |
| 3 | 69 |
| 4 | 253 |
| 5 | 1049 |
| 6 | 4205 |
| 7 | 16887 |
| 8 | 68015 |
| 9 | 273471 |
| 10 | 1100135 |
| 11 | 4425449 |
| 12 | 17801365 |
| 13 | 71607677 |
| 14 | 288046417 |
| 15 | 1158686263 |
| 16 | 4660895899 |
| 17 | 18748771139 |
| 18 | 75418217399 |
| 19 | 303374944277 |
| 20 | 1220346484777 |
| 21 | 4908927310389 |
| 22 | 19746496259789 |
| 23 | 79431633434755 |
[3,15,69,253,1049,4205,16887,68015,273471,1100135, 4425449,17801365,71607677,288046417,1158686263, 4660895899,18748771139,75418217399,303374944277, 1220346484777,4908927310389,19746496259789, 79431633434755] |