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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 0 |
| 4 | 36 |
| 5 | -60 |
| 6 | 1920 |
| 7 | -1680 |
| 8 | 109200 |
| 9 | -347760 |
| 10 | 9858240 |
| 11 | -27941760 |
| 12 | 1321911360 |
| 13 | -3675672000 |
| 14 | 210819248640 |
| 15 | -422918496000 |
| 16 | 45482678841600 |
| 17 | 432259027200 |
| 18 | 11915705273472000 |
| 19 | 32436011672064000 |
| 20 | 3902063601673036800 |
| 21 | 25891695005316940800 |
| 22 | 1575143884245502771200 |
[1,1,4,0,36,-60,1920,-1680,109200,-347760,9858240, -27941760,1321911360,-3675672000,210819248640, -422918496000,45482678841600,432259027200, 11915705273472000,32436011672064000, 3902063601673036800,25891695005316940800, 1575143884245502771200] |