Sn=n(n+2) 求1/S1+1/S2+...Sn=
已知Sn=1/2n(n+1),Tn=S1+S2+S3+.+Sn,求Tn.
设数列{an}前n项和为Sn,已知(1/S1)+(1/S2)+.+(1/Sn)=n/(n+1),求S1,S2及Sn
Sn=n^2+2n 求1/S1+1/S2+1/S3+……+1/Sn
sn=n^2 求证1/s1+1/s2+1/s3……1/sn
已知s1=1,s2=1+2,s3=1+2+3,.sn=1+2+3+.+n,求Dn=s1+s2+s3,.sn
an=3n,Sn为前n项和,求1/S1+1/S2+1/S3+…+1/Sn.
设sn为数列an的前n项和,Sn=(-1)^n-1/2^n,n属于N*,则(1)a3=? (2)S1+S2+...+S1
高中数学数列证明已知Sn=2^n-1证明:n/2 - 1/3 < S1/S2 + S2/S3 +.+ Sn/Sn+1 <
等差数列前n项和Sn=(-1)^nAn-1/2^n 求 S1+S2+S3+……+S100
S1+S2+S3+……+S2008=?Sn=1/2×【(1-n/n)+(n/n+1)】 S1=4/1,S2=7/12,S
设数列{an}前n项和为Sn,若s1=1,s2=2,且Sn+1-3Sn+2Sn-1=0(n>=2,求AN
已知数列{an}的前n项的和为Sn,且1/S1+1/S2+ +1/Sn=n/(n+1) (1)求S1,S2及Sn.