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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 7 |
| 5 | 15 |
| 6 | 105 |
| 7 | 855 |
| 8 | 7855 |
| 9 | 55975 |
| 10 | 560065 |
| 11 | 8413815 |
| 12 | 92433795 |
| 13 | 1445733485 |
| 14 | 21748130145 |
| 15 | 378156976785 |
| 16 | 6718626421035 |
| 17 | 128657800331555 |
| 18 | 2540367695055365 |
| 19 | 57535394030907155 |
| 20 | 1264457062012294015 |
[1,1,1,7,15,105,855,7855,55975,560065,8413815, 92433795,1445733485,21748130145,378156976785, 6718626421035,128657800331555,2540367695055365, 57535394030907155,1264457062012294015] |