已知数列{an}中,a1=1,前n项和sn=（n+2/3）an,求an的通项公式,

当n≥2,an=Sn-Sn-1=[(n+2)*an]/3-[(n+1)*an-1]/3an/an-1=(n+1)/(n-1)（a2/a01）*（a3/a2)……*（an-1/an-2）*(an/an-1）=an=（3/1）*（4/2）……*[n/(n-2)]*(n+1)/(n-1)==n(n+1)/2当n=1,S1=a1=1符合an所以an=n(n+1)/...