при любом целом n>1:
\frac{1}{2n}+\frac{1}{2n}+...+\frac{1}{2n}=n*\frac{1}{2n}=\frac{1}{2}" alt="\frac{1}{n+1}+\frac{1}{n+2}+...+\frac{1}{2n}>\frac{1}{2n}+\frac{1}{2n}+...+\frac{1}{2n}=n*\frac{1}{2n}=\frac{1}{2}" align="absmiddle" class="latex-formula">