等差数列1+2+3+...+2n有几项
有关等差数列的数学题已知等差数列{an},{bn}的前n项和分别为Sn,Tn,且Sn/Tn=(3n+2)/(2n+1),
已知数列An是各项均为正数的等差数列,lga1,lga2,lga4成等差数列,又Bn=1/A(2^n),n=1,2,3,
等差数列{an}前n项和为Sn=3n-2n^2,求an
已知等差数列前n项和 sn=2n^2+3n求an
12n+2分之n(n-1)在乘以2=242是等差数列的...
等差数列-7/2,-3,-5/2,-2,··第n+1项为多少?
等差数列an=2n+3,求和:(1/a1a2)+(1/a2a3)+.+(1/anan+1)
S[n]是等比数列{a[n]}前n项和,若S[1],2S[2],3S[3]成等差数列,求证:{a[n]}公比是1/3
已知等差数列{an}满足a(n+1)=an+3n+2,且a1=2,求an.
nS(n+1)〖角标〗-(n+1)Sn=n^2+n 且S1、S2/2、S3/3为等差数列 a1=1
等差数列1/2,-1/3-7/6,...前n项的绝对值之和为50,则n=
等差数列{an},{bn}的前n项和分别为An,Bn,切An/Bn=2n/3n+1,求lim(n→∞)an/bn