Ramanujan theta function

English

Etymology

Named after mathematician Srinivasa Ramanujan.

Proper noun

the Ramanujan theta function

1. (mathematics) A theta function that generalizes the form of the Jacobi theta functions while capturing their general properties. It is defined as: $f(a,b)=\sum _{n=-\infty }^{\infty }a^{\frac {n(n+1)}{2}}\;b^{\frac {n(n-1)}{2}}$ for |ab| < 1.