x^(3n+1)y^(n-1)+2x^(2n+1)y^(2n-1)+x^(n+1)y^(3n-1
=x^(n+1)y^(n-1)[x^(2n)+2x^ny^n+y^(2n)]
=x^(n+1)y^(n-1)[x^n+y^n)^2