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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | -1 |
| 3 | 3 |
| 4 | -6 |
| 5 | 23 |
| 6 | -135 |
| 7 | 1036 |
| 8 | -8820 |
| 9 | 79253 |
| 10 | -783405 |
| 11 | 8594146 |
| 12 | -103172454 |
| 13 | 1341998591 |
| 14 | -18791767995 |
| 15 | 281865510928 |
| 16 | -4509653027880 |
| 17 | 76663767284201 |
| 18 | -1379952916274457 |
| 19 | 26219142105604030 |
| 20 | -524382882377053690 |
[0,0,-1,3,-6,23,-135,1036,-8820,79253,-783405, 8594146,-103172454,1341998591,-18791767995, 281865510928,-4509653027880,76663767284201, -1379952916274457,26219142105604030, -524382882377053690] |