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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 21 |
| 6 | 112 |
| 7 | 853 |
| 8 | 11117 |
| 9 | 261080 |
| 10 | 11716571 |
| 11 | 1006700565 |
| 12 | 164059830476 |
| 13 | 50335907869219 |
| 14 | 29003487462848061 |
| 15 | 31397381142761241960 |
| 16 | 63969560113225176176277 |
| 17 | 245871831682084026519528568 |
| 18 | 1787331725248899088890200576580 |
| 19 | 24636021429399867655322650759681644 |
[1,1,1,2,6,21,112,853,11117,261080,11716571, 1006700565,164059830476,50335907869219, 29003487462848061,31397381142761241960, 63969560113225176176277, 245871831682084026519528568, 1787331725248899088890200576580, 24636021429399867655322650759681644] |