如果是把“1/(3*5)+”换成“1/(5*8)+”就对了2,5,8,11,14,17,20,23..顺序增加31/(2*5)+1/(5*8)+1/(8*11)+...+1/(20*23)＝(1/3)*(1/2-1/5+1/5-1/8+1/8-1/11+.+1/20-1/23)=(1/3)*(1/2-1/23)=7/46