急用!数列{an}满足a1=1,a3+a7=18.
急用!数列{an}满足a1=1,a3+a7=18.
已知数列an满足a1=1,a3+a7=18
已知等差数列{an}公差为d,满足a1+a2+a3=15,且a1+1,a3+1,a7+1构成等你数列的连续三项
已知数列an满足a1=1,a3+a7=18,且(an-1)+(an+1)=2an(n>=2)
已知数列{an}满足a1=1,a3+a7=18,且an-1+an+1=2an(n≥2).
已知数列{an}满足a1=1,a3+a7=18,且an-1+an+1=2an(n大于等于2) (1)求数列(an)的通项
已知数列{an}满足a1+a2+a3+...+an=n^2+2n.(1)求a1,a2,a3,a4
已知等差数列{an}中,a1=1,a7=4,数列{bn}是等比数列,b1=6,b2=a3.
数列{an}满足:1/a1+2/a2+3/a3+…+n/an=2n
数列an满足a1+2a2+3a3+...+nan=(n+1)(n+2) 求通项an
已知数列{An}满足A1=1,A3+A7=18,且A(n-1)+A(n+1)=2An若Cn=2^n-1*An,求{Cn}
等比数列{an}满足a1+a2=3,a2+a3=6,则a7=______.