1 q 2 + 1 q 4 − 1 q 5 + 1 q 6 − 1 q 7 {\displaystyle {\frac {1}{q^{2}}}+{\frac {1}{q^{4}}}-{\frac {1}{q^{5}}}+{\frac {1}{q^{6}}}-{\frac {1}{q^{7}}}}