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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 6 |
| 4 | 56 |
| 5 | 720 |
| 6 | 11880 |
| 7 | 240240 |
| 8 | 5765760 |
| 9 | 160392960 |
| 10 | 5079110400 |
| 11 | 180503769600 |
| 12 | 7117005772800 |
| 13 | 308403583488000 |
| 14 | 14572069319808000 |
| 15 | 745747076954880000 |
| 16 | 41098950018846720000 |
| 17 | 2427001153744527360000 |
| 18 | 152901072685905223680000 |
[1,6,56,720,11880,240240,5765760,160392960, 5079110400,180503769600,7117005772800, 308403583488000,14572069319808000, 745747076954880000,41098950018846720000, 2427001153744527360000,152901072685905223680000] |