解:n=1时,a1=S1=a1(a1-1)a1(a1-2)=0Sn≠0,a1=S1≠0,因此只有a1=2n≥2时,an=Sn-S(n-1)=a1(an-1)-a1[a(n-1)-1]an=2(an-1)-2[a(n-1)-1]整理,得an=2a(n-1)an/a(n-1)=2,为定值数列{an}是以2为首项,2为公比的等比数列an=2·2ⁿ⁻¹=2ⁿn=1时,a1=2,同样满足表达式数列{an}的通项公式为an=2ⁿ