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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 9 |
| 4 | 25 |
| 5 | 59 |
| 6 | 129 |
| 7 | 271 |
| 8 | 557 |
| 9 | 1131 |
| 10 | 2281 |
| 11 | 4583 |
| 12 | 9189 |
| 13 | 18403 |
| 14 | 36833 |
| 15 | 73695 |
| 16 | 147421 |
| 17 | 294875 |
| 18 | 589785 |
| 19 | 1179607 |
| 20 | 2359253 |
| 21 | 4718547 |
| 22 | 9437137 |
| 23 | 18874319 |
| 24 | 37748685 |
| 25 | 75497419 |
| 26 | 150994889 |
| 27 | 301989831 |
| 28 | 603979717 |
| 29 | 1207959491 |
| 30 | 2415919041 |
[0,2,9,25,59,129,271,557,1131,2281,4583,9189, 18403,36833,73695,147421,294875,589785,1179607, 2359253,4718547,9437137,18874319,37748685, 75497419,150994889,301989831,603979717,1207959491, 2415919041] |