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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 7 |
| 3 | 20 |
| 4 | 60 |
| 5 | 182 |
| 6 | 547 |
| 7 | 1641 |
| 8 | 4921 |
| 9 | 14762 |
| 10 | 44286 |
| 11 | 132860 |
| 12 | 398581 |
| 13 | 1195743 |
| 14 | 3587227 |
| 15 | 10761680 |
| 16 | 32285040 |
| 17 | 96855122 |
| 18 | 290565367 |
| 19 | 871696101 |
| 20 | 2615088301 |
| 21 | 7845264902 |
| 22 | 23535794706 |
| 23 | 70607384120 |
| 24 | 211822152361 |
| 25 | 635466457083 |
| 26 | 1906399371247 |
| 27 | 5719198113740 |
[1,3,7,20,60,182,547,1641,4921,14762,44286,132860, 398581,1195743,3587227,10761680,32285040,96855122, 290565367,871696101,2615088301,7845264902, 23535794706,70607384120,211822152361,635466457083, 1906399371247,5719198113740] |