$$\prod\limits_{k = 1}^{ + \infty } {\left( {1 + {u^{k - 1}}{v^k}} \right)\left( {1 + {u^k}{v^{k - 1}}} \right)\left( {1 - {u^k}{v^k}} \right)} = \sum\limits_{q = - \infty }^{ + \infty } {{u^{\frac{{q\left( {q + 1} \right)}}{2}}}{v^{\frac{{q\left( {q - 1} \right)}}{2}}}} $$