已知数列an的前n项和为Sn,a1=1,若n≥2时,an是Sn与S(n-1)的等差中项(注:n-1是下标),则a5=?
已知数列an的前n项和为Sn,a1=1,若n≥2时,an是Sn与S(n-1)的等差中项(注:n-1是下标),则a5=?
已知:数列{an}的前n项和为Sn,a1=3且当n≥2n∈N+满足Sn-1是an与-3的等差中项.
快,已知数列An的前n项和为Sn,且满足An+2Sn*S(n-1)=0,n>=2,a1=1/2.求1,数列1/Sn是等差
数列An的前n项和为Sn,已知A1=1,An+1=Sn*(n+2)/n,证明数列Sn/n是等比数列
已知数列{An}的前n项和为Sn,且Sn是An与1的等差中项,则An=
已知数列{an}的前n项和为Sn,a1=-23,Sn+1Sn=an-2(n≥2,n∈N)
设Sn是数列an的前n项和,已知a1=1,an=-Sn*Sn-1,(n大于等于2),则Sn=
已知数列{an}的首相a1=1,a2=3,前n项和为Sn,且Sn+1(下标)、Sn、Sn-1(下标)(n≥2)满足(Sn
数列an的前n项和为Sn,a1=1/4且Sn=Sn-1+an-1+1/2(n-1为下标)
已知数列{an}的首项a1=5,前n项和为Sn.若Sn+1=2Sn+n+5(n∈N*),则数列{an+1}是等比数列.
设数列{an}的前n项和为Sn,已知Sn=2an-2n+1,(n为下标,n+1为上标),求通项公式?
已知数列{an}的首项a1=3,前n项和为Sn,且S(n+1)=3Sn+2n(n∈N)