若Sn=1-2+3-4+…+(-1)n-1•n,S17+S33+S50等于______.
1.在等差数列{an}中,a9=5,则a1+a17等于多少?S17等于多少?2.已知数列{an}中Sn=n(n-1),则
设Sn=-1+3-5+7-…+(-1)n(2n-1),则Sn=______.
已知等差数列{an}的前n项和为Sn,若S33−S1=1,则数列{an}的公差是( )
已知等差数列{an}的前n项和为Sn,且满足S33-S22=1,则数列{an}的公差是( )
Sn=n(n+2)(n+4)的分项等于1/6[n(n+2)(n+4)(n+5)-(n-1)n(n+2)(n+4)]吗?
已知数列{an}前n项和为Sn,若Sn=2n-1,则a8=______.
数列{an}的前n项之和Sn=n2+3n+1,则a1+a3+a5等于______.
已知a1=3,an=Sn-1+2^n(n大于等于2),求an,Sn?
数列{an}的前n项和为Sn,若a1=1,an+1=3Sn(n≥1),则a6=______.
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}的前n项和为Sn=1+2+3+4+…+n,求f(n)= Sn /(n+32)Sn+1的最大值
已知数列{an}的前n项和为Sn,满足Sn=2an+n2-4n(n=1,2,3,…).