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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | -2 |
| 3 | 4 |
| 4 | -12 |
| 5 | 68 |
| 6 | -440 |
| 7 | 3064 |
| 8 | -26208 |
| 9 | 265936 |
| 10 | -2945152 |
| 11 | 35730176 |
| 12 | -485182720 |
| 13 | 7235106240 |
| 14 | -115677206528 |
| 15 | 1984468240000 |
| 16 | -36707903762432 |
| 17 | 725871298851072 |
| 18 | -15190637885095936 |
| 19 | 336136505074527232 |
[0,1,-2,4,-12,68,-440,3064,-26208,265936,-2945152, 35730176,-485182720,7235106240,-115677206528, 1984468240000,-36707903762432,725871298851072, -15190637885095936,336136505074527232] |