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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | -1 |
| 3 | 3 |
| 4 | -6 |
| 5 | 23 |
| 6 | -90 |
| 7 | 91 |
| 8 | 2520 |
| 9 | -37549 |
| 10 | 453600 |
| 11 | -4950539 |
| 12 | 46054008 |
| 13 | -322939255 |
| 14 | 209249040 |
| 15 | 58871058247 |
| 16 | -1726916711520 |
| 17 | 36675055548935 |
| 18 | -665460508297536 |
| 19 | 10471928861164609 |
| 20 | -129836456400150520 |
[0,0,-1,3,-6,23,-90,91,2520,-37549,453600, -4950539,46054008,-322939255,209249040, 58871058247,-1726916711520,36675055548935, -665460508297536,10471928861164609, -129836456400150520] |