4、. B. C. D.解析:选C 借助递推关系,将a8逆推依次得到a7=,a6=,a5=.故选C.7.(xx·宝鸡检测)已知数列{an}满足a1=1,a2=3,an+1·an-1=an(n≥2),则a2013的值等于( )A.3 B.1 C. D.32013解析:选A 由已知得an+1=,an+3==÷an+1=,故an+6==an,所以,该数列是周期为6的数列,所以a2013=a3=3.故选A.8.(xx·嘉兴质检)已知数列{an}满足a1=1,an+1an=2n(n∈N*),则a10=( )A.64 B.32 C.16