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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | -1 |
| 3 | 3 |
| 4 | -6 |
| 5 | 23 |
| 6 | -150 |
| 7 | 1351 |
| 8 | -12600 |
| 9 | 118187 |
| 10 | -1217160 |
| 11 | 14287141 |
| 12 | -188257608 |
| 13 | 2702562653 |
| 14 | -41510829360 |
| 15 | 680290364755 |
| 16 | -11907404789280 |
| 17 | 222160337026823 |
| 18 | -4398121126494144 |
| 19 | 91965696132459313 |
[0,0,-1,3,-6,23,-150,1351,-12600,118187,-1217160, 14287141,-188257608,2702562653,-41510829360, 680290364755,-11907404789280,222160337026823, -4398121126494144,91965696132459313] |