设等比数列an满足：a1=1/3,a2+a3=4/27,且an＞0,求数列an的通项公式,设bn=n/an,求数列bn的前n项和Sn

等差数列{an}满足a1=1,且a1、a2、a4成等比数列,求an 等比数列an满足 lim(a1+a2+a3+...+an)=1/2 求a1取值范围 设数列｛An｝满足 A1=6,A2=4 A3=3,且数列{An+1-An}（n属于自然数）是等差数列,球An的通向公式 rt设数列｛An｝满足 A1=6,A2=4 A3=3,且数列{An+1-An}（n属于自然数）是等比数列,球An的通向公式rt 已知等比数列{an}满足a1+a2=3,a2+a3=6,则a7= 已知等比数列an满足a1+a2=3,a2+a3=6,则a7=? 已知等比数列{an}满足a1+a2=3,a2+a3=6,则a7=（ ） 已知等比数列{An}满足a1+a2=3,a2+a3=6,求a7 设等比数列an满足：a1=1/3,a2+a3=4/27,且an＞0,求数列an的通项公式,设bn=n/an,求数列bn的前n项和Sn 设数列AN满足A1等于1,3(A1+a2+~+AN)=(n+2)an,求通向公式 若等比数列{an}满足a1+a2=3,a3+a4=12,则a1+a2+a3+……+an= 设各项均为正数的数列{an}和{bn}满足:an,bn,an+1成等差数列,bn,an+1,bn+1等比数列且a1=1,b1=2,a2=3求通项an,bn 设各项均为正数的数列｛an}和｛bn}满足：an,bn,an+1成等差数列,bn,an+1,bn+1成等比数列,且a1=1,b1=2,a2=3,求通项an,bn 设数列an的前n项和为Sn,满足an+Sn=An^2+Bn+1（A不等于0）,a1=3/2,a2=9/4,求证an-n为等比数列并求an 设数列{an}{bn}满足a1=b1=6 a2=b2=4 a3=b3=3若{an+1 - an}为等差数列.{bn+1 -bn}为等比数列.分别求{an}{bn}的通项公式. 已知等比数列an中,满足a1+a2=3,a2+a3=6,则数列{An+An+1}的前8项和 若数列｛an｝满足a1,a2-a1,a3-a2,...是以1为首相,3为公比的等比数列,则an______ 求{bn}的通项公式已知等差数列{an}的首项a1=1,a6=3a2,等比数列{bn}满足b1=a1,b2=a2. 设数列{an}满足lg(1+a1+a2+...+an)=n+1,求通项公式an