What comes after calculus 3 and differential equations and linear algebra

Not counting statistics and probability.

Information theory and signal processing, Mathematical physics, Dynamical systems and differential equations, Geometry and topology, among others

depends upon the university where you are studying......

partial DE , complex variables , modern algebra , applied mathematics ,

pure mathematics , topology , numerical analysis , geometry , history of mathematics,

functional analysis , vector and tensor analysis , etc...that is why students need guidance