sn=n^2 求证1/s1+1/s2+1/s3……1/sn

sn=n^2 求证1/s1+1/s2+1/s3……1/sn An=2n-1,求证1/s1+1/s2+1/s3+…+1/sn Sn=n^2 证明1/S1+1/S2+. 已知Sn=n^2,Tn=1/S1+1/S2+1/S3+...+1/Sn,求证TnTn sn是数列an的前n项和 且sn+an=2n+1 求证数列an-2是等比数列 求和s1+s2+L+sn 已知sn=(17n-n^2)/2求：1/s1+1/s2+…+1/sn Sn=n(n+2) 求1/S1+1/S2+...Sn= 已知数列an中 an>0 2√sn=an+1 前n项和为sn求证1/s1+1/s2+1/s3+...+1/sn 设Sn=2+4+6+.+2n,则1/s1+1/s2+.+1/sn= Sn=1/2n ,求证s1^2+s2^2+s3^2+.+sn^2≤1/2 - 1/4n据说是用放缩法~可我不大懂 已知数列{an}的前n项和sn=1/2n求证;s1+s2+s3+……+sn各自平方的和 < 7/16即已知数列{an}的前n项和sn=1/2n求证;s1^2+s2^2+s3^2+…+sn^2各自平方的和< 7/16 已知s1=1,s2=1+2,s3=1+2+3,.sn=1+2+3+.+n,求Dn=s1+s2+s3,.sn 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+2n 求1/S1+1/S2+1/S3+……+1/Sn Sn=(n^2)/2+n/2,Tn=1/S1+1/S2+...+1/Sn,求Tn 等差数列{an}=2n+1,前n项和为Sn,求1/S1+1/S2+.+1/Sn 若Sn=n乘(n+2),怎么才能证明1/S1+2/S2+3/S3+…+1/Sn 已知数列an=2n+1求1/s1+1/s2+...+1/sn的值