1/3+1/8+1/15+1/24+...+1/360=3=1X3 8=2X4 15=3X5 24=4X6 360=18X20

1/3=1/(1*3)=1/2*(1-1/3)1/8=1/(2*4)=1/2*(1/2-1/4)1/15=1/(3*5)=1/2*(1/3-1/5)1/24=1/(4*6)=1/2*(1/4-1/6).1/323=1/(17*19)=1/2*(1/17-1/19)1/360=1/(18*20)=1/2*(1/18-1/20)1/3+1/8+1/15+1/24+...+1/360=1/2*[(1-1...