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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | -3 |
| 4 | 15 |
| 5 | -90 |
| 6 | 662 |
| 7 | -5712 |
| 8 | 56688 |
| 9 | -635616 |
| 10 | 7944640 |
| 11 | -109494880 |
| 12 | 1649256800 |
| 13 | -26948575680 |
| 14 | 474694809920 |
| 15 | -8965921171200 |
| 16 | 180743109203200 |
| 17 | -3873060672256000 |
| 18 | 87906536803046400 |
| 19 | -2106613788720768000 |
[0,0,1,-3,15,-90,662,-5712,56688,-635616,7944640, -109494880,1649256800,-26948575680,474694809920, -8965921171200,180743109203200,-3873060672256000, 87906536803046400,-2106613788720768000] |