Data:7 3/HOMFLYPT Polynomial

${\frac {z^{4}}{a^{4}}}+{\frac {z^{4}}{a^{6}}}+{\frac {3z^{2}}{a^{4}}}+{\frac {3z^{2}}{a^{6}}}-{\frac {z^{2}}{a^{8}}}+{\frac {1}{a^{4}}}+{\frac {2}{a^{6}}}-{\frac {2}{a^{8}}}$