题目有错,应该是大于2/3
1/(n+1)>1/3n
1/(n+2)>1/3n
...
1/(n+1)+1/(n+2)+1/(n+3)+·····+1/3n
>1/3n+1/3n+.+1/3n
=2n/3n=2/3
n是自然数,求证1/(n+1)+1/(n+2)+1/(n+3)+·····+1/3n
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