令 S(n) = 1+1/2+1/3+1/4+1/5+1/6+...1/n,
则 S(∞) = 1 + (1/2+1/3) + (1/4+1/5+1/6+1/7) + ...
< 1 + (1/2+1/2) + (1/4+1/4+1/4+1/4) + ...
且 S(∞) = 1 + 1/2 +(1/3+1/4) + (1/5+1/6+1/7+1/8) + ...
> 1 + 1/2 +(1/4+1/4) + (1/8+1/8+1/8+1/8) + ...
可推证:1 + k/2 < S(n) < 1 + k,其中 k = log(ln)/log(2),n> 2
从上式,可看出S(n)不收敛.
当n> 40时,更接近S(n)上限