Largest PhD programs in mathematics

I'll be applying to graduate schools in the fall but so far don't have any real clue what area I want to focus on. As such, I hope to attend a very large math graduate program with a lot of varied research going on so that there are many avenues I can explore. I also worry that if I attend a small or midsize graduate school, I may come to find out that my true passion is in an topic for which there are no suitable advisers. I also think I'd fit in much better in a larger department.

I'm interested in a list of PhD math programs by number of students. So I've done some googling, but I can't find any relavant results. What are the largest math graduate programs in the US?