数列an中,a1=1/4 ,当n>=2时,有(3n^2-2n-1)an=a1+a2+a3+.+a(n-1)

(3n^2-2n-1)an=a1+a2+a3+.+a(n-1)[3(n-1)^2-2(n-1)-1]an-1=a1+a2+a3+.+a(n-2)两式相减(3n^2-2n-1)an-[3(n-1)^2-2(n-1)-1]a(n-1)=a(n-1)(3n^2-2n-1)an=[3n^2-6n+3-2n+2-1+1]a(n-1)(3n^2-2n-1)an=[3n^2-8n+5]a(n-1)(3n...