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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | -1 |
| 3 | 6 |
| 4 | -22 |
| 5 | 140 |
| 6 | -976 |
| 7 | 8456 |
| 8 | -83952 |
| 9 | 957840 |
| 10 | -12249856 |
| 11 | 174293856 |
| 12 | -2725714432 |
| 13 | 46514037440 |
| 14 | -859767771136 |
| 15 | 17115342333056 |
| 16 | -365039421683712 |
| 17 | 8304761365213440 |
| 18 | -200743169243938816 |
| 19 | 5137820023434733056 |
| 20 | -138802582805546401792 |
| 21 | 3947233200665413667840 |
[0,1,-1,6,-22,140,-976,8456,-83952,957840, -12249856,174293856,-2725714432,46514037440, -859767771136,17115342333056,-365039421683712, 8304761365213440,-200743169243938816, 5137820023434733056,-138802582805546401792, 3947233200665413667840] |