=1+ 1-1/2 + 1-1/3 + 1-1/4.+1-1/(n+1)=n+1-1/2-1/3-1/4-1/5.-1/(n+1)=n+n/(n+1)-(1/2+1/3+1/4+1/5+1/6+.+1/n)=(n的平方+2n)/(n+1)-(1/2+1/3+1/4+1/5+1/6+.+1/n)只能算到这了