6,7,19,31,71,?

1/21/31/41/51/6

1/2+1/3+1/4+1/5+1/6+1/7+1/8+1/9+1/10+1/11 =1/2+1/3+1/2*1/2+1/5+1/2*1/3+1/7+1/2*1/2*1/2+1/3*1/3+1/2*1*5+1/11 =1/2(1+1/2+1/3+1/4)+1/3(1+1/3)+1/5(1+1/2)+1/7+1/11 =1/2*25/12+1/3*4/3+1/5*3/2+18/77 =25/24+5/3+3/10+18/77 =25/24+40/24+411/770 =65/24+411/770 =29957/9240 。 全部

   1/2+1/3+1/4+1/5+1/6+1/7+1/8+1/9+1/10+1/11 =1/2+1/3+1/2*1/2+1/5+1/2*1/3+1/7+1/2*1/2*1/2+1/3*1/3+1/2*1*5+1/11 =1/2(1+1/2+1/3+1/4)+1/3(1+1/3)+1/5(1+1/2)+1/7+1/11 =1/2*25/12+1/3*4/3+1/5*3/2+18/77 =25/24+5/3+3/10+18/77 =25/24+40/24+411/770 =65/24+411/770 =29957/9240 。
  收起