0 = (3*n^3+18*n^2+33*n+18+(-9*n^3-89*n^2-274*n-264)*N+(9*n^3+123*n^2+552*n+792)
*N^2+(-3*n^3-51*n^2-311*n-634)*N^3+(-n^2+12*n+71)*N^4+(-16*n-84)*N^5+(4*n+24)*N
^6)*x_n