Sn=n(n+2) 求1/S1+1/S2+...Sn=
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已知sn=(17n-n^2)/2求:1/s1+1/s2+…+1/sn
Sn=n(n+2) 求1/S1+1/S2+...Sn=
Sn=n^2 证明1/S1+1/S2+.
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急
Sn=(n^2)/2+n/2,Tn=1/S1+1/S2+...+1/Sn,求Tn
Sn=n^2+2n 求1/S1+1/S2+1/S3+……+1/Sn
等差数列{an}=2n+1,前n项和为Sn,求1/S1+1/S2+.+1/Sn
已知数列an=2n+1求1/s1+1/s2+...+1/sn的值
an=0.2n+2.8.求1/S1+2/S2+…1/Sn
已知s1=1,s2=1+2,s3=1+2+3,.sn=1+2+3+.+n,求Dn=s1+s2+s3,.sn
等差数列前n项和Sn=(-1)^nAn-1/2^n 求 S1+S2+S3+……+S100
设Sn=2+4+6+.+2n,则1/s1+1/s2+.+1/sn=
sn=n^2 求证1/s1+1/s2+1/s3……1/sn
an=3n,Sn为前n项和,求1/S1+1/S2+1/S3+…+1/Sn.
S1=1,S2=1+2,S3=1+2+3,…SN=1+2+3+…+N求S1+S2+S3+…+S130这里急!
若Sn=n乘(n+2),怎么才能证明1/S1+2/S2+3/S3+…+1/Sn
数列求和:Sn=(2n-1)除以2的n-1次方Tn=s1+s2+s3+…sn求Tn
数列an中,a1=-2/3,sn+1/sn=an-2(n>1的整数),求s1,s2,s3,猜想sn表达式,并证明