a(n+1)=(2an^2+3an+1)/(an+1)=(2an+1)(an+1)/(an+1)=2an+1,a1=1,a2=2*(1+1)-1=2^2-1,a(n+1)=2an+1=2[2a(n-1)+1]+1=4a(n-1)+2+1=4[2a(n-2)+1]+2+1=8a(n-2)+4+2+1=......=2^n a1+2^(n-1)+......+4+2+1=2^n+2^(n-1)+...+2^2+2+1,所以an=2^n-1