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| n | a(n) |
|---|---|
| 3 | 1 |
| 4 | 18 |
| 5 | 105 |
| 6 | 1005 |
| 7 | 6762 |
| 8 | 61572 |
| 9 | 558548 |
| 10 | 5807700 |
| 11 | 62757288 |
| 12 | 777291768 |
| 13 | 9831740256 |
| 14 | 139111566048 |
| 15 | 2048834965824 |
| 16 | 32758018496640 |
| 17 | 545051532176640 |
| 18 | 9812211976039680 |
| 19 | 182219827628874240 |
| 20 | 3627461543458659840 |
| 21 | 74765368810365696000 |
| 22 | 1632210845693218560000 |
[1,18,105,1005,6762,61572,558548,5807700,62757288, 777291768,9831740256,139111566048,2048834965824, 32758018496640,545051532176640,9812211976039680, 182219827628874240,3627461543458659840, 74765368810365696000,1632210845693218560000] |