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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 18 |
| 4 | 91 |
| 5 | 592 |
| 6 | 4643 |
| 7 | 42276 |
| 8 | 436629 |
| 9 | 5033182 |
| 10 | 63974273 |
| 11 | 888047414 |
| 12 | 13358209647 |
| 13 | 216334610860 |
| 14 | 3751352135263 |
| 15 | 69325155322184 |
| 16 | 1359759373992105 |
| 17 | 28206375825238458 |
| 18 | 616839844140642301 |
| 19 | 14181213537729200474 |
| 20 | 341879141423814854915 |
| 21 | 8623032181189674581256 |
[1,2,5,18,91,592,4643,42276,436629,5033182, 63974273,888047414,13358209647,216334610860, 3751352135263,69325155322184,1359759373992105, 28206375825238458,616839844140642301, 14181213537729200474,341879141423814854915, 8623032181189674581256] |