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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | -1 |
| 3 | -6 |
| 4 | -31 |
| 5 | -140 |
| 6 | -625 |
| 7 | -2170 |
| 8 | -2623 |
| 9 | 96072 |
| 10 | 1642975 |
| 11 | 23520882 |
| 12 | 295668001 |
| 13 | 3935469564 |
| 14 | 50912723823 |
| 15 | 723034935870 |
| 16 | 10169862858113 |
| 17 | 159490471907856 |
| 18 | 2472265829827775 |
| 19 | 43176564012771434 |
[1,0,-1,-6,-31,-140,-625,-2170,-2623,96072, 1642975,23520882,295668001,3935469564,50912723823, 723034935870,10169862858113,159490471907856, 2472265829827775,43176564012771434] |