a1=1,2an+1=(1+1/n)^2*an 证明{an/n^2}为等比数列 求{an}通项公式 令bn=（an+1）,求数列{bn}的前n项和Sn

an=a1+(n-1)d 和Sn=n(a1+an)/2中an是什么意思? an=a1+(n-1)d 和Sn=n(a1+an)/2中an是什么 数列{An}满足a1=1/2,a1+a2+..+an=n方an,求an 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 a1=1,Sn=n^2an,求an 设a1,a2,...,an都是正数,证明不等式(a1+a2+...+an)[1/(a1)+1/(a2)+...+1/(an)]>=n^2 已知数列{An}满足A1=0.5,A1+A2+…+An=n^2An(n∈N*),试用数学归纳法证明:An=1/n(n+1) 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}满足a1=2,a(n+1)=2an+n+2,求an a1=5,n大于等于2时,an-an-1=6n,求an 数列an,a1=1.an+1/an=n+2/n,求通项公式, 已知数列｛an｝中,a(n+1)=an+2^n,a1=3,求an