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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 27 |
| 5 | 76 |
| 6 | 210 |
| 7 | 589 |
| 8 | 1659 |
| 9 | 4708 |
| 10 | 13428 |
| 11 | 38479 |
| 12 | 110682 |
| 13 | 319411 |
| 14 | 924339 |
| 15 | 2681410 |
| 16 | 7794939 |
| 17 | 22702396 |
| 18 | 66229212 |
| 19 | 193495279 |
| 20 | 566069052 |
| 21 | 1658026093 |
| 22 | 4861703289 |
| 23 | 14269842184 |
| 24 | 41922504570 |
| 25 | 123265254451 |
| 26 | 362719839225 |
| 27 | 1068105234304 |
[0,1,3,10,27,76,210,589,1659,4708,13428,38479, 110682,319411,924339,2681410,7794939,22702396, 66229212,193495279,566069052,1658026093, 4861703289,14269842184,41922504570,123265254451, 362719839225,1068105234304] |