已知{an}是等差数列,a1+a2+a3+a4=11,an-3+an-2+an-1+an=67且sn=286求项数n?
已知{an}是等差数列,a1+a2+a3+a4=11,an-3+an-2+an-1+an=67且sn=286求项数n?
已知数列{an}的前n项和sn=n^2+2n+3,求和1/a1+a2+1/a2+a3+1/a3+a4+.+1/an+an
已知数列an,an>0,Sn=a1+a2+a3.+an,且an=6Sn/an + 3,求Sn!
等差数列{an}中,a1+a2+a3=21,an-2+an-1+an=57,Sn=520,求n.
已知数列{an}满足:a1=1,且an-an-1=2n,求(1)a2,a3,a4.(2)求数列{an}的通项an
数列an满足sn=3an-1/2 计算a1,a2,a3,a4 猜an通项 求an前n项和sn
已知数列an的前n项和为sn,且sn+an=1/2(n2+5n+2)(2属于n*) 计算a1 a2 a3 a4
在数列{an}中,已知a1=1/3,a1+a2+.+an/n=(2n-1)an (1)求,a2,a3,a4,并猜想an的
数列{an}的前n项和为sn且a1=1 an+1=1/3sn求a2,a3,a4及an
已知数列an为等差数列,an=n,则a1*a2-a2*a3+a3*a4-a4*a5+...-a100*a101=
已知等差数列an,前n项和Sn,且a3>a2,a2a3=45,a1+a4=14.(1)bn=Sn/(n+c),若bn
已知数列{an}满足:a1=1,且an-a(n-1)=2n.求a2,a3,a4.求数列{an}通项an