若数列{an} a2=2 a6=0 且{1／（an+1）}是等差数列,则a4=多少

若数列{an} a2=2 a6=0 且{1／（an+1）}是等差数列,则a4=多少
若数列{an} a2=2 a6=0 且{1／（an+1）}是等差数列,则a4=多少

若数列{an} a2=2 a6=0 且{1／（an+1）}是等差数列,则a4=多少
数列{1/an+1}是等差数列 1/(a4+1)-1/(a2+1)=1/(a6+1)-1/(a4+1) 2/(a4+1)=1/(2+1)+1/(0+1)=4/3 a4=1/2.