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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 60 |
| 4 | 280 |
| 5 | 3780 |
| 6 | 74844 |
| 7 | 576576 |
| 8 | 6949800 |
| 9 | 110416020 |
| 10 | 3319141540 |
| 11 | 31333878576 |
| 12 | 545777101324 |
| 13 | 8349081650000 |
| 14 | 196469122903200 |
| 15 | 8108831645948160 |
| 16 | 99934219113287400 |
| 17 | 1961077012271694900 |
| 18 | 39215221761564594900 |
| 19 | 860948656518718429200 |
| 20 | 25274389422461123124180 |
[1,0,0,60,280,3780,74844,576576,6949800,110416020, 3319141540,31333878576,545777101324,8349081650000, 196469122903200,8108831645948160, 99934219113287400,1961077012271694900, 39215221761564594900,860948656518718429200, 25274389422461123124180] |