q^(4 + 4*n) - q^(8 + 7*n) - q^(10 + 9*n) + q^(12 + 12*n) + 
 (q^(16 + 15*n) - q^(16 + 16*n))*f[n] + (-1 + q^(2 + n))*f[2 + n]
