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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 20 |
| 4 | 90 |
| 5 | 430 |
| 6 | 2136 |
| 7 | 10937 |
| 8 | 57307 |
| 9 | 305822 |
| 10 | 1656482 |
| 11 | 9083432 |
| 12 | 50328114 |
| 13 | 281324294 |
| 14 | 1584578746 |
| 15 | 8984740485 |
| 16 | 51242962251 |
| 17 | 293772468164 |
| 18 | 1691974930584 |
| 19 | 9785378133297 |
| 20 | 56805049768157 |
| 21 | 330880419984832 |
| 22 | 1933299689139364 |
| 23 | 11328101469158554 |
[1,1,5,20,90,430,2136,10937,57307,305822,1656482, 9083432,50328114,281324294,1584578746,8984740485, 51242962251,293772468164,1691974930584, 9785378133297,56805049768157,330880419984832, 1933299689139364,11328101469158554] |