Just to clarify, I recommend the book "Probability and Computing" but the course I'm recommending is normally called something along the lines of "Combinatorics and Discrete Probability" at most universities. So the online course isn't as far off base as it may have looked. However, I agree there are better choices that cover more exactly what I want. So I've updated it with a more on-point Harvard Extension course.

The MIT and CMU courses both cover combinatorics and discrete probability. They are probably the right thing to take or very close to it if you're at those particular schools.

Thanks again for the feedback Klao.