设Sn=-1+3-5+7-…+(-1)n(2n-1),则Sn=______.
设Sn=-1+3-5+7-…+(-1)n(2n-1),则Sn=______.
设Sn是数列an的前n项和,已知a1=1,an=-Sn*Sn-1,(n大于等于2),则Sn=
Sn=1x2+3x2^2+5x2^3+…+(2n-1)x2^n sn=2sn-sn
1 设Sn=1+2+3……+n,则f(n)=Sn/((n+7)*S(n+1))的最大值为
设Sn是等差数列{an}(n∈N+)的前n项和,且a1=1,a4=7,则S5=______.
设Sn为等差数列{an}的前n项和,若a1=1,公差d=2,Sn+2-Sn=36,则n=( )
Sn=3+2^n Sn-1=3+2^(n-1).则Sn-Sn-1=?
已知数列{an}的首项是a1=1,前n项和为Sn,且Sn+1=2Sn+3n+1(n∈N*).
已知数列{an}的首项a1=5,前n项和为Sn,且Sn+1=2Sn+n+5(n∈N*).
设数列{an}的前n项和为Sn,且2an=Sn+2n+1(n∈N*).
已知数列an的首项a1=5,前n项和为Sn,且S(n+1)=2Sn+n+5(n∈N*),求数列{an}的前n项和Sn,设
设数列{an}的前n项和为Sn,已知a1+2a2+3a3+…+nan=(n-1)Sn+2n (n∈N*).