\frac{{q; q}_{a_{n} + a_{1} + a_{2} + \dots}}{\dots ({q; q}_{a_{1}}) ({q; q}_{a_{2}}) ({q; q}_{a_{n}})}  in x_{1}^{0} x_{2}^{0} \dots coeff . of x_{n}^{0} \prod_{1 \leq j < k \leq n} ({\frac{x_{j}}{x_{k}}; q}_{a_{j}}) ({\frac{q x_{k}}{x_{j}}; q}_{a_{k}})