What are some of the most useful Math courses to take for CS?

[Hash_HofM]

Hi all, 

 

I'll be starting next year at a public R1 university with majors in Mathematics and Computer Science (and possibly a minor in Econ) with a number of math credits I earned through dual enrollment during high school (Calc 1, Calc 2, Calc 3, Diff Eq's, Intro to Analysis, and Modern Crypto). I've been reading through my university's course progression, prereq flowchart, etc and quickly realized that I am very much a fish out of water when it comes to selecting courses to take during my undergrad.

Based on the little contact I've had with a departmental advisor, I'd be able to start on a Master's degree (albeit forced to) at my university for Math in my Junior/Senior years if I want to be able to continue to take graduate math classes beyond the 2 that my university allows for undergrads.

My question is basically this, what Math/CS courses (undergraduate/graduate) do you all recommend I take in order to put myself in a good position for applying to top20 grad schools as a prospective math PhD?

In terms of a future career, it'd be interesting to work as a research quant in a WSB.