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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | -1 |
| 3 | 1 |
| 4 | -6 |
| 5 | 15 |
| 6 | -105 |
| 7 | 390 |
| 8 | -3500 |
| 9 | 15785 |
| 10 | -188685 |
| 11 | 946350 |
| 12 | -15864750 |
| 13 | 90057825 |
| 14 | -2127610485 |
| 15 | 15254857800 |
| 16 | -444774915000 |
| 17 | 4213468013625 |
| 18 | -130378398500025 |
| 19 | 1538133793366950 |
| 20 | -48054409884965250 |
[0,0,-1,1,-6,15,-105,390,-3500,15785,-188685, 946350,-15864750,90057825,-2127610485,15254857800, -444774915000,4213468013625,-130378398500025, 1538133793366950,-48054409884965250] |