1/2+1/3+2/3+1/4+2/4+3/4+1/5+2/5+3/5+4/5+1/6+……+1/60+2/60+3/60+……+59/60
=(1/2)+(1/3+2/3)+(1/4+2/4+3/4)+...+(1/60+2/60+...+59/60)
通式為1/2+1/3+2/3+1/4+2/4+3/4+1/5+2/5+3/5+4/5+1/6+……+1/a+2/a+...+(a-1)/a
=(1/2)+(2/2)+(3/2)+...+((a-1)/2)
=(1+2+3+4+...+(a-1))/2
=(1+2+3+4+..+59)/2
=59(1+59)/4
=59*15
=885