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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 14 |
| 4 | 56 |
| 5 | 280 |
| 6 | 1872 |
| 7 | 11760 |
| 8 | 104832 |
| 9 | 1224720 |
| 10 | 12545280 |
| 11 | 96526080 |
| 12 | 1163289600 |
| 13 | 13891046400 |
| 14 | 200222668800 |
| 15 | 2917119744000 |
| 16 | 47259168768000 |
| 17 | 738275586048000 |
| 18 | 13386781384704000 |
| 19 | 259936372452556800 |
| 20 | 5427242941317120000 |
[1,3,14,56,280,1872,11760,104832,1224720,12545280, 96526080,1163289600,13891046400,200222668800, 2917119744000,47259168768000,738275586048000, 13386781384704000,259936372452556800, 5427242941317120000] |