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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 28 |
| 5 | 101 |
| 6 | 342 |
| 7 | 1189 |
| 8 | 4088 |
| 9 | 14121 |
| 10 | 48682 |
| 11 | 167969 |
| 12 | 579348 |
| 13 | 1998541 |
| 14 | 6893822 |
| 15 | 23780349 |
| 16 | 82029808 |
| 17 | 282961361 |
| 18 | 976071762 |
| 19 | 3366950329 |
| 20 | 11614259468 |
| 21 | 40063270581 |
| 22 | 138197838502 |
| 23 | 476712029909 |
| 24 | 1644413252328 |
| 25 | 5672386654201 |
[0,1,2,9,28,101,342,1189,4088,14121,48682,167969, 579348,1998541,6893822,23780349,82029808, 282961361,976071762,3366950329,11614259468, 40063270581,138197838502,476712029909, 1644413252328,5672386654201] |