I am a year away from completing an undergrad degree in Computer Science and I find myself increasingly interested in more advanced subjects from pure mathematics that sometimes lie outside the scope of my major, and I think I would enjoy doing graduate work in pure math. But I feel like the amount of formal education I've had the opportunity to have in my undergrad isn't quite sufficient for graduate work in math.
If I were to go and buy a book or two on some subject I'd like to learn more about that I can't take a course on (say, Abstract Algebra or Number Theory), and spend this summer getting comfortable with it, is it likely that a graduate admission committee take my efforts into account?
My situation is worded specific to a CS --> Pure Math trajectory, but it's part of a more general question. Do graduate school admissions take into account personal study, or do they only care about formal university education?