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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | -1 |
| 3 | 3 |
| 4 | -15 |
| 5 | 120 |
| 6 | -1530 |
| 7 | 27630 |
| 8 | -609570 |
| 9 | 15061950 |
| 10 | -401747850 |
| 11 | 11409145650 |
| 12 | -343436893650 |
| 13 | 10953453262050 |
| 14 | -370722834699750 |
| 15 | 13349217937623750 |
| 16 | -512802860608788750 |
| 17 | 21056741300679288750 |
| 18 | -924609697617056519250 |
| 19 | 43346843603808212081250 |
| 20 | -2162059111418145178443750 |
[1,1,-1,3,-15,120,-1530,27630,-609570,15061950, -401747850,11409145650,-343436893650, 10953453262050,-370722834699750,13349217937623750, -512802860608788750,21056741300679288750, -924609697617056519250,43346843603808212081250, -2162059111418145178443750] |