( q t + 1 1 − t ) ( 1 + s 2 t 2 + s 4 t 4 + q s 2 t 4 + q t 2 ) {\displaystyle \left({\frac {{q}{t}+1}{1-t}}\right)(1+s^{2}t^{2}+s^{4}t^{4}+{q}s^{2}t^{4}+{q}t^{2})}
