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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -4 |
| 2 | 2 |
| 3 | -4 |
| 4 | -21 |
| 5 | -136 |
| 6 | -996 |
| 7 | -8152 |
| 8 | -73811 |
| 9 | -733244 |
| 10 | -7938186 |
| 11 | -93126716 |
| 12 | -1178054657 |
| 13 | -15998857056 |
| 14 | -232339375664 |
| 15 | -3594982133808 |
| 16 | -59070662442383 |
| 17 | -1027605845674036 |
| 18 | -18873206761567638 |
| 19 | -365015243426704372 |
| 20 | -7416392564276075453 |
| 21 | -157957992952546414328 |
[1,-4,2,-4,-21,-136,-996,-8152,-73811,-733244, -7938186,-93126716,-1178054657,-15998857056, -232339375664,-3594982133808,-59070662442383, -1027605845674036,-18873206761567638, -365015243426704372,-7416392564276075453, -157957992952546414328] |