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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | -3 |
| 4 | 13 |
| 5 | -70 |
| 6 | 447 |
| 7 | -3297 |
| 8 | 27576 |
| 9 | -257904 |
| 10 | 2667240 |
| 11 | -30226680 |
| 12 | 372517920 |
| 13 | -4960668960 |
| 14 | 70986162240 |
| 15 | -1086347505600 |
| 16 | 17705365171200 |
| 17 | -306178316236800 |
| 18 | 5599477712102400 |
| 19 | -107980208561433600 |
| 20 | 2189837602616832000 |
[0,0,1,-3,13,-70,447,-3297,27576,-257904,2667240, -30226680,372517920,-4960668960,70986162240, -1086347505600,17705365171200,-306178316236800, 5599477712102400,-107980208561433600, 2189837602616832000] |