1.已知等差数列(an)的前n项和为Sn,bn=1/Sn,且a3+a5=21 2已知等比数列{an}满足an>0,n=1
1.已知等差数列(an)的前n项和为Sn,bn=1/Sn,且a3+a5=21 2已知等比数列{an}满足an>0,n=1,2等,且a5*a(2n-5)=2的2n次方,则当n≥1时log2a1+log2a3+..+log2a(2n-1)=多少 3.an=2n-1 .bn的前n项和为Tn=1-1/2bn,若cn=(3的n次方*bn)/an*a(n+1),Sn为cn的前n项和,证明:Sn<1