All math majors take calculus.
All math majors take a course in linear algebra.
All math majors take a course in probability.
All math majors take at least one proof course.

All math majors take additional math courses, depending on the particular degree option they choose.
Some math major options require or allow certain courses in other departments as part of the major.

And, of course, all math majors (like all majors) take "area courses" in English, Government, Language, History, Humanities, Science, and Social Science.

Calculus classes are usually large (lectures with about 120 students, with discussion sections of about 40 students, led by a TA), but after that the only large classes are Advanced Calculus for Applications II (Differential Equation), which most math majors take, and Advanced Calculus for Applications II (Advanced Multivariable Calculus), which not too many math majors take. Most of the other math classes have 20 to 40 students in each section.

For more details:
    Descriptions of Math Major Degree Options
    More Detail on Courses Required for each Degree Option