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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 20 |
| 6 | 60 |
| 7 | 189 |
| 8 | 613 |
| 9 | 2039 |
| 10 | 6918 |
| 11 | 23850 |
| 12 | 83315 |
| 13 | 294282 |
| 14 | 1049279 |
| 15 | 3771685 |
| 16 | 13653313 |
| 17 | 49730599 |
| 18 | 182130129 |
| 19 | 670274170 |
| 20 | 2477514172 |
| 21 | 9193599339 |
| 22 | 34237330355 |
| 23 | 127914531260 |
| 24 | 479318575375 |
| 25 | 1800971051420 |
| 26 | 6783809423496 |
| 27 | 25611913597250 |
| 28 | 96903193235645 |
| 29 | 367363376407250 |
[1,1,1,3,7,20,60,189,613,2039,6918,23850,83315, 294282,1049279,3771685,13653313,49730599, 182130129,670274170,2477514172,9193599339, 34237330355,127914531260,479318575375, 1800971051420,6783809423496,25611913597250, 96903193235645,367363376407250] |