Sn=11−12+13−⋅⋅⋅+(−1)n−1×1n{S_n=\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{3}-···+(-1)^{n-1}\times\dfrac{1}{n}}Sn=11−21+31−⋅⋅⋅+(−1)n−1×n1 错了
应该是 Sn=11−12+13−⋅⋅⋅+(n−1)−1×1n{S_n=\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{3}-···+(n-1)^{-1}\times\dfrac{1}{n}}Sn=11−21+31−⋅⋅⋅+(n−1)−1×n1 或者是 Sn=11−12+13−⋅⋅⋅+dfrac1n−1×1n{S_n=\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{3}-···+dfrac{1}{n-1}\times\dfrac{1}{n}}Sn=11−21+31−⋅⋅⋅+dfrac1n−1×n1
