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| n | a(n) |
|---|---|
| 0 | -1 |
| 1 | 1 |
| 2 | -2 |
| 3 | 0 |
| 4 | 24 |
| 5 | -240 |
| 6 | 1440 |
| 7 | -5040 |
| 8 | -40320 |
| 9 | 1088640 |
| 10 | -14515200 |
| 11 | 119750400 |
| 12 | 0 |
| 13 | -24908083200 |
| 14 | 610248038400 |
| 15 | -9153720576000 |
| 16 | 62768369664000 |
| 17 | 1422749712384000 |
| 18 | -70426110763008000 |
| 19 | 1703031405723648000 |
| 20 | -24329020081766400000 |
| 21 | -51090942171709440000 |
[-1,1,-2,0,24,-240,1440,-5040,-40320,1088640, -14515200,119750400,0,-24908083200,610248038400, -9153720576000,62768369664000,1422749712384000, -70426110763008000,1703031405723648000, -24329020081766400000,-51090942171709440000] |