（1/8+1/24+1/48+1/80+1/120+1/168+1/224+1/288）*128
=[1/8+1/2(1/4-1/6+1/6-1/8+1/8-1/10+1/10-1/12+1/12-1/14+1/14-1/16+1/16-1/18)]*128
=[1/8+1/2*(1/4-1/18)]*128
=128*1/8+128*1/2*1/4-128*1/2*1/18
=16+16-32/9
=32又9分之8