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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 7 |
| 5 | 39 |
| 6 | 207 |
| 7 | 1437 |
| 8 | 11203 |
| 9 | 99041 |
| 10 | 975645 |
| 11 | 10601377 |
| 12 | 125905445 |
| 13 | 1622349059 |
| 14 | 22539777113 |
| 15 | 335845307359 |
| 16 | 5341990288103 |
| 17 | 90340567900583 |
| 18 | 1618553943500599 |
| 19 | 30623660893656205 |
| 20 | 610152486797080443 |
| 21 | 12769086757046132625 |
[0,1,0,3,7,39,207,1437,11203,99041,975645, 10601377,125905445,1622349059,22539777113, 335845307359,5341990288103,90340567900583, 1618553943500599,30623660893656205, 610152486797080443,12769086757046132625] |