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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 20 |
| 5 | 77 |
| 6 | 310 |
| 7 | 1287 |
| 8 | 5507 |
| 9 | 23997 |
| 10 | 106461 |
| 11 | 478855 |
| 12 | 2179053 |
| 13 | 10013878 |
| 14 | 46395636 |
| 15 | 216471174 |
| 16 | 1016036750 |
| 17 | 4793581181 |
| 18 | 22717231101 |
| 19 | 108081903944 |
| 20 | 516000919269 |
| 21 | 2471019949777 |
| 22 | 11865491405235 |
| 23 | 57115582866293 |
| 24 | 275534745299842 |
| 25 | 1331860105355623 |
| 26 | 6449424864465372 |
| 27 | 31281905895224367 |
[1,1,2,6,20,77,310,1287,5507,23997,106461,478855, 2179053,10013878,46395636,216471174,1016036750, 4793581181,22717231101,108081903944,516000919269, 2471019949777,11865491405235,57115582866293, 275534745299842,1331860105355623,6449424864465372, 31281905895224367] |