1 q 9 / 2 − 1 q 7 / 2 + 1 q 21 / 2 − 1 q 19 / 2 + 1 q 17 / 2 − 2 q 15 / 2 + 1 q 13 / 2 − 2 q 11 / 2 {\displaystyle {\frac {1}{q^{9/2}}}-{\frac {1}{q^{7/2}}}+{\frac {1}{q^{21/2}}}-{\frac {1}{q^{19/2}}}+{\frac {1}{q^{17/2}}}-{\frac {2}{q^{15/2}}}+{\frac {1}{q^{13/2}}}-{\frac {2}{q^{11/2}}}}
