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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 8 |
| 3 | 20 |
| 4 | 49 |
| 5 | 119 |
| 6 | 290 |
| 7 | 714 |
| 8 | 1781 |
| 9 | 4507 |
| 10 | 11580 |
| 11 | 30208 |
| 12 | 79941 |
| 13 | 214327 |
| 14 | 581292 |
| 15 | 1592496 |
| 16 | 4400765 |
| 17 | 12251895 |
| 18 | 34326566 |
| 19 | 96694866 |
| 20 | 273639617 |
| 21 | 777444807 |
| 22 | 2216341466 |
| 23 | 6336999666 |
| 24 | 18165573373 |
| 25 | 52191551315 |
| 26 | 150254448730 |
| 27 | 433350470586 |
[1,3,8,20,49,119,290,714,1781,4507,11580,30208, 79941,214327,581292,1592496,4400765,12251895, 34326566,96694866,273639617,777444807,2216341466, 6336999666,18165573373,52191551315,150254448730, 433350470586] |