(1887-1920)
-
,
where

and for each positive integer k,

.
-
.
-
.
.
.
.
.
.
.
, for all
, where
is the Gamma Function.
- Define
, which is called Ramanujan Theta Function. Special values include

.

.
- Ramanujan’s Master Theorem

then

for small of x = 0.
References
Berndt, B. C. Ramanujan's Notebooks: Part I. New York: Springer-Verlag, 1985.
Berndt, B. C. Ramanujan's Notebooks: Part II. New York: Springer-Verlag, 1989.
Berndt, B. C. Ramanujan's Notebooks, Part IV. New York: Springer-Verlag, 1994.
Berndt, B. C. and Bhargava, S. ``A Remarkable Identity Found in Ramanujan's Third Notebook.'' Glasgow Math. J, 1992.
D.V. Chudnovsky and G.V. Chudnovsky. Approxiamtions and Complex Multiplication According to Ramanujan. San Diego, CA: Academic Press, 1988.