One advantage Wesleyan has is that you don’t have to take a bus or train to enroll in graduate courses: I counted 38 mid to upper level math courses in the 2015-2016 Wesleyan catalogue, including 11 at the 500 (PhD) level:
https://iasext.wesleyan.edu/regprod/!wesmaps_page.html?crse_list=MATH&offered=Y