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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | -6 |
| 4 | 36 |
| 5 | -240 |
| 6 | 1920 |
| 7 | -17640 |
| 8 | 183120 |
| 9 | -2116800 |
| 10 | 26943840 |
| 11 | -374220000 |
| 12 | 5628934080 |
| 13 | -91122071040 |
| 14 | 1579034096640 |
| 15 | -29155689763200 |
| 16 | 571308920582400 |
| 17 | -11838533804697600 |
| 18 | 258608278645516800 |
| 19 | -5938673374272038400 |
| 20 | 143003892952893772800 |
[1,0,2,-6,36,-240,1920,-17640,183120,-2116800, 26943840,-374220000,5628934080,-91122071040, 1579034096640,-29155689763200,571308920582400, -11838533804697600,258608278645516800, -5938673374272038400,143003892952893772800] |