1/3+2/8+2/15+2/24+2/35+2/48+2/63+2/80

嗯,原式=2（1/8+1/24+1/48+1/80）+2（1/15+1/35+1/63）+1/3=2[1/（2*4）+1/（4*6）+1/（6*8）+1/（8*10)]+2[1/(3*5)+1/(5*7)+1/(7*9)]+1/3=[1/2-1/4+1/4-1/6+1/6-1/8+1/8-1/10]+[1/3-1/...