<p>What kind of background do you have? Classes like Harvard 55 don’t do you any good if you fail it, or fail all your other classes trying to pass it. The intro math sequences are going to be filled with previous IMO/USAMO winners, people that have already taken multiple college math classes, etc. You really should make sure you have the mathematical maturity, intellect, and dedication to succeed in those types of classes. I’ve heard that Princeton’s intro honors math sequence assumes you’ve already seen a fair amount of theoretical math.</p>