How to dress for visit to math phd program for accepted students? How should I dress for my visits to math programs as an accepted student?  As if I were showing up to a job interview?  Shirt and tie?  Suit?

The visit seems nicely planned by the program - jam-packed with meetings and events with faculty and students.

(I'd guess that this visit would also be a great time to talk to faculty to see who could be a great match for me as an advisor.)
Math professors tend to be pretty casual dressers compared to those in other disciplines. Wearing khaki pants and a collared shirt (polo or button down) would put one towards the dressier end of the spectrum at most places, and jeans and a t-shirt / hoody are usually unlikely to cause one to stand out. 

I think that if you were to wear a suit and tie to these events you’d stand out. Not in a negative way mind you, it’s just that all of the faculty members you’ll be interacting with will be dressed much more casually. If you wear jeans or khakis with a collared shirt and sweater then you’ll look like you put in some effort and are taking this seriously, but aren’t dressed up so formally that you stand out.