an=(1/2+...+1/2^(2n-1))Sn=2/3 • (1-1(1/2)^2n)

数列{an}满足a1=1 an+1=2n+1an/an+2n 数列｛an},a1=1,an+1=2an-n^2+3n,求｛an｝. 数列{an}中,a1=1,an+1/an=n/n+2,求an 在{an}中an>0 Sn=1/2（an+n/an）求an 已知数列｛an｝中a1=6,且an-an-1=(an-1/n)+n+1(n属于N*,n≥2）,求an 数列{an}中,a1=2,an+1=4an-3n+1,求证{an-n}是等比数列 4an中n为下标an+1中n+1为下标an-n中an的n为下标 已知数列an中,a1=1,an/an-1=n+1/n,n大于等于2,求an 设an=(1/n+1)+(1/n+2)+(1/n+3)+...+1/2n,则an+1-an等于? 已知an=n/(2^n),bn=ln(1+an)+1/2 an^2,证明,对一切n∈N*,2/(2+an)＜an/bn成立 数列{an}满足a1=2,a(n+1)=2an+n+2,求an An=1/n^2 数列求和An=1/n^2 数列(An)求和 已知A1=1,An=2An-1+n（n>1）,求An. an=an-1+2的n次方+n,a1=1,an=? 数列an满足a1=1/3,Sn=n(2n-1)an,求an 数列{an}中,a1=2,an+1=an+ln(n+1/n),求通项公式 数列{an},a1=3,an*a(n+1)=(1/2)^n,求an 数列an中,若a（ n+1）=an+(2n-1)求an a1=5,n大于等于2时,an-an-1=6n,求an