In his famous deathbed letter, Ramanujan introduced the notion of a
mock theta function
, and he offered some alleged examples. Recent work by Zwegers [Zwegers S (2001)
Contemp Math
291:268–277 and Zwegers S (2002) PhD thesis (Univ of Utrecht, Utrecht, The Netherlands)] has elucidated the theory encompassing these examples. They are
holomorphic parts
of special harmonic weak Maass forms. Despite this understanding, little attention has been given to Ramanujan’s original definition. Here, we prove that Ramanujan’s examples do indeed satisfy his original definition.