数列{an}满足a1=a2=1,an+an+1+an+2=cos2nπ/3若数列{an}的前n项和为sn则s2013的值数列{an}满足a1=a2=1,a（n)+a（n+1）+a（n+2）=cos(2nπ/3),n∈N*.若数列{an}的前n项和为Sn则S2013的值为?答案是-671/2 (n),(n+1),(n+2)都是

数列{An}满足a1=1/2,a1+a2+..+an=n方an,求an 已知数列满足a1=1/2,an+1=2an/(an+1),求a1,a2已知数列满足a1=1/2,a(n+1)=2an/(an+1),求a1,a2;证明0 已知数列an满足an=1+2+...+n,且1/a1+1/a2+...+1/an 设数列{an}满足lg(1+a1+a2+...+an)=n+1,求通项公式an 数列an满足a1=1/2,a1+a2+a3……an=n^2an,则an 已知数列{an}中满足a1=1,a(n+1)=2an+1 (n∈N*),证明a1/a2+a2/a3+…+an/a(n+1) (1)数列{an}中,a1=1,a2=-3,a(n+1)=an+a(n+2),则a2005=____(2)已知数列｛an｝满足a1=1,a1×a2×a3…an=n^2,求an. 已知数列{an}满足a1=1,a2=3,an+2=3an+1-2an求an 已知数列{an}满足条件:a1=5,an=a1+a2+...a(n-1) n大于等于2,求数列{an}的通项公式 已知数列｛an｝满足：a1=1,且an-a（n-1）=2n.求a2,a3,a4.求数列｛an｝通项an 已知数列{an}满足a1=a,a2=b,a(n+1)=a(n+2)+an,求a2012 已知数列{an}满足a(n+2)=a(n+1)-an,a1=1,a2=2,求a2005 已知数列{an}满足a1=1,a2=3,a(n+2)=a(n+1)-an,求S2012 已知数列{an}满足,a1=1,a2=2,a(n+1)=a(n+2)+an,求a2011? 已知数列{an}满足a1+a2+...+an=n²an求其通项an 已知数列an'满足a1=1/2,a1+a2+a3+...+an=n^2an,求通项公式 设数列AN满足A1等于1,3(A1+a2+~+AN)=(n+2)an,求通向公式 已知数列{an}满足关系式lg（1+a1+a2+.+an）=n,求数列{an}的通项公式