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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 6 |
| 3 | 18 |
| 4 | 42 |
| 5 | 108 |
| 6 | 274 |
| 7 | 692 |
| 8 | 1754 |
| 9 | 4442 |
| 10 | 11248 |
| 11 | 28488 |
| 12 | 72146 |
| 13 | 182712 |
| 14 | 462728 |
| 15 | 1171876 |
| 16 | 2967826 |
| 17 | 7516146 |
| 18 | 19034954 |
| 19 | 48206826 |
| 20 | 122085820 |
| 21 | 309187486 |
| 22 | 783030352 |
| 23 | 1983057390 |
| 24 | 5022176478 |
| 25 | 12718873752 |
| 26 | 32211084212 |
| 27 | 81575929322 |
| 28 | 206594481604 |
[3,6,18,42,108,274,692,1754,4442,11248,28488, 72146,182712,462728,1171876,2967826,7516146, 19034954,48206826,122085820,309187486,783030352, 1983057390,5022176478,12718873752,32211084212, 81575929322,206594481604] |