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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -24 |
| 2 | 252 |
| 3 | -1520 |
| 4 | 5982 |
| 5 | -18240 |
| 6 | 57320 |
| 7 | -198192 |
| 8 | 604389 |
| 9 | -1567840 |
| 10 | 4210116 |
| 11 | -12229632 |
| 12 | 32349958 |
| 13 | -77844000 |
| 14 | 196563240 |
| 15 | -510760752 |
| 16 | 1233110610 |
| 17 | -2871650184 |
| 18 | 6899741020 |
| 19 | -16499031456 |
| 20 | 37934952672 |
| 21 | -86122235648 |
[1,-24,252,-1520,5982,-18240,57320,-198192,604389, -1567840,4210116,-12229632,32349958,-77844000, 196563240,-510760752,1233110610,-2871650184, 6899741020,-16499031456,37934952672,-86122235648] |