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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | -1 |
| 3 | -2 |
| 4 | 6 |
| 5 | 25 |
| 6 | -165 |
| 7 | -366 |
| 8 | 6188 |
| 9 | 5573 |
| 10 | -294885 |
| 11 | -813034 |
| 12 | 35950266 |
| 13 | -141917555 |
| 14 | -1041102153 |
| 15 | -22047494262 |
| 16 | 843256939320 |
| 17 | -9500491668343 |
| 18 | 83224830490839 |
| 19 | -2409782172431474 |
| 20 | 68273680978437710 |
| 21 | -1275838005728358495 |
[0,1,-1,-2,6,25,-165,-366,6188,5573,-294885, -813034,35950266,-141917555,-1041102153, -22047494262,843256939320,-9500491668343, 83224830490839,-2409782172431474, 68273680978437710,-1275838005728358495] |