记数列{an}的前n项和为Sn,若{Sn/an}是公差为d的等差数列,则{an}为等差数列的充要条件是d=?
记数列{an}的前n项和为Sn,若{Sn/an}是公差为d的等差数列,则{an}为等差数列的充要条件是d=?
等差数列an中,公差d>0,且a5+a10=0,记数列-2/an的前n项和为Sn,则使Sn
已知{An}是公差为d的等差数列,它的前n项和为Sn,S4=2S2+4,Bn=1+An/An 求d
已知公差不为0的等差数列{An}的首项A1=1,前n项和为Sn,若数列{Sn/An}是等差数列,求An?
若等差数列{an}的首项为a1,公差为d,前n项的和为Sn,则数列(Sn/n)为等差数列,且通项
{an}为等差数列,公差d>0,Sn是数列{an}前n项和,
已知{An}是公差为d的等差数列,它的前n项的和为Sn,S4=2S2+4,bn=(1+An)/An
已知{an}是公差为d的等差数列,它的前n项和为Sn,S4=2S2+4,bn=(1+an)/an.
设Sn为等差数列{an}的前n项和,若a1=1,公差d=2,Sn+2-Sn=36,则n=( )
设等差数列an的公差为d不等于0,前n项和为Sn.则Sn为递增数列的充分必要条件是
设等差数列an的公差d为2,前n项和为Sn,则lim(an^2-n^2)/Sn=?
设公差为d的等差数列{an}的前n项和为Sn,若a1=1,-2/17