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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | -2 |
| 3 | 3 |
| 4 | -3 |
| 5 | 10 |
| 6 | -56 |
| 7 | 315 |
| 8 | -1971 |
| 9 | 13788 |
| 10 | -105246 |
| 11 | 857615 |
| 12 | -7266223 |
| 13 | 61296222 |
| 14 | -465353292 |
| 15 | 1982748495 |
| 16 | 36246192441 |
| 17 | -1600097656520 |
| 18 | 43901543199046 |
| 19 | -1078930450441413 |
| 20 | 25757481055625541 |
| 21 | -615789512284527630 |
[1,0,-2,3,-3,10,-56,315,-1971,13788,-105246, 857615,-7266223,61296222,-465353292,1982748495, 36246192441,-1600097656520,43901543199046, -1078930450441413,25757481055625541, -615789512284527630] |