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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 8 |
| 3 | 60 |
| 4 | 816 |
| 5 | 17520 |
| 6 | 550080 |
| 7 | 23839200 |
| 8 | 1365799680 |
| 9 | 100053999360 |
| 10 | 9127781913600 |
| 11 | 1015061950425600 |
| 12 | 135193044668774400 |
| 13 | 21248464632595200000 |
| 14 | 3891825697262043340800 |
| 15 | 821745573997874093568000 |
| 16 | 198152975926832672858112000 |
| 17 | 54121124248225908770856960000 |
| 18 | 16621698830590738881776812032000 |
[2,8,60,816,17520,550080,23839200,1365799680, 100053999360,9127781913600,1015061950425600, 135193044668774400,21248464632595200000, 3891825697262043340800,821745573997874093568000, 198152975926832672858112000, 54121124248225908770856960000, 16621698830590738881776812032000] |