1×4,2×5,3×6,.前n项和Sn
数列an的前n项和Sn满足Sn=3n+1,n≤5,Sn=n^2,n≥6,求通项公式
设数列1*4,2*5,3*6,n*(n+3),前n项和sn=
求数列4,9,16,.,3n-1+2^n,.前n项的和Sn
已知数列{an}的前n项和为Sn=1+2+3+4+…+n,求f(n)= Sn /(n+32)Sn+1的最大值
设Sn为数列{an}的前n项和,且有S1=a,Sn+Sn-1=3n²,n=2,3,4,.
已知an=5n(n+1)(n+2)(n+3),求数列{an}的前n项和Sn
已知等差数列{an}的前n项和为Sn,且(2n-1)Sn+1 -(2n+1)Sn=4n²-1(n∈N*)
已知数列前n项和为Sn=1+2+2+3+3+3+4+4+4+4+5+5+5+5+.+n+n+n+n+n+.n,求Sn
已知Sn为数列{an}的前n项和,且Sn=2an+n²-3n-2,n=1,2,3,4,5......1.
数列{an}前n项和为Sn,且2Sn+1=3an,求an及Sn
求数列{(2n-1)*1/4的n次方}的前n项和Sn
已知数列{an}的首项a1=5,前n项和为Sn,且Sn+1=2Sn+n+5(n∈N*).