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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | -487 |
| 3 | -19558 |
| 4 | -261519 |
| 5 | -1950000 |
| 6 | -10062071 |
| 7 | -40275482 |
| 8 | -133827103 |
| 9 | -385467364 |
| 10 | -990234375 |
| 11 | -2309119566 |
| 12 | -4915639727 |
| 13 | -9383796248 |
| 14 | -14557531159 |
| 15 | -7925781250 |
| 16 | 83868413889 |
| 17 | 644351576628 |
| 18 | 3616337975257 |
| 19 | 18750798630346 |
[1,4,-487,-19558,-261519,-1950000,-10062071, -40275482,-133827103,-385467364,-990234375, -2309119566,-4915639727,-9383796248,-14557531159, -7925781250,83868413889,644351576628, 3616337975257,18750798630346] |