q 13 − 4 q 12 + 9 q 11 − 15 q 10 + 20 q 9 − 23 q 8 + 23 q 7 − 21 q 6 + 16 q 5 − 10 q 4 + 6 q 3 − 2 q 2 + q {\displaystyle q^{13}-4q^{12}+9q^{11}-15q^{10}+20q^{9}-23q^{8}+23q^{7}-21q^{6}+16q^{5}-10q^{4}+6q^{3}-2q^{2}+q}
