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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | -1 |
| 3 | 3 |
| 4 | 2 |
| 5 | -20 |
| 6 | -40 |
| 7 | 630 |
| 8 | -3092 |
| 9 | 13032 |
| 10 | -133580 |
| 11 | 1827980 |
| 12 | -21237632 |
| 13 | 244445760 |
| 14 | -3154775208 |
| 15 | 45173375520 |
| 16 | -689191245168 |
| 17 | 11093076554048 |
| 18 | -189142200382672 |
| 19 | 3415285850672880 |
| 20 | -65041019882791840 |
| 21 | 1301902345882783680 |
[1,0,-1,3,2,-20,-40,630,-3092,13032,-133580, 1827980,-21237632,244445760,-3154775208, 45173375520,-689191245168,11093076554048, -189142200382672,3415285850672880, -65041019882791840,1301902345882783680] |