Ramanujan theta function
From specialfunctionswiki
Let $|ab|<1$. The Ramanujan theta function $f$ is defined by $$f(a,b)=\displaystyle\sum_{k=-\infty}^{\infty} a^{\frac{k(k+1)}{2}} b^{\frac{k(k-1)}{2}}.$$
Let $|ab|<1$. The Ramanujan theta function $f$ is defined by $$f(a,b)=\displaystyle\sum_{k=-\infty}^{\infty} a^{\frac{k(k+1)}{2}} b^{\frac{k(k-1)}{2}}.$$
