等差数列列｛an｝的前n项和为Sn,公差为2,则lim(n→∞)Sn/an^2=?

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=? 等差数列列｛an｝的前n项和为Sn,公差为2,则lim(n→∞)Sn/an^2=? 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 等差数列{an}的前n项和为Sn,公差d 记数列an前n项和为Sn,数列Sn/an是公差为d的等差数列,则数列an为等差数列时,d=1/2 和1 已知{an}是首项为19,公差为-2的等差数列,Sn为｛an｝的前n项和, 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? 已知等差数列an的公差为d,前n项和Sn＝－n^2,则通项公式为 已知等差数列{an}的首项为4,公差为4,其前n项和为Sn,则数列{1/Sn}的前n项和为 设等差数列{an}公差d是2,前n项和为Sn,则lim(an^2-n^2)/Sn 设等差数列{an}公差d是2,前n项和为Sn,则lim(an^2-n^2)/Sn 数列前n项和为sn,a1=1,an+sn是公差为2的等差数列,求an-2是等比数列,并求sn 等差数列An的首项为a1等于3公差等于2前n项和为Sn求数列.1/Sn的前n项和Tn 设数列{an}的前n项和为Sn,若{an}和{根号sn+n}都是公差为d的等差数列,则a1= 谢谢）在等差数列{an}中,设公差为d,若前n项和Sn=-n²;,则{an}的通项公式和公差分别 设公差为d的等差数列{an}的前n项和为Sn,若a1=1,-2/17 等差数列｛an｝前n项和为Sn,且Sn=3n^2+n 求公差d 已知等差数列an中a1=2,其前n项和sn,若数列｛Sn/n｝构成一个公差为2的等差数列,则a3=?