If you think you might be interested in graduate school in mathematics after you finish your mathematics major at Dartmouth, then I strongly encourage you to come in and talk. The simple truth is that you can't take too much mathematics to prepare for graduate school. Just meeting the minimum requirements for the major is not good preparation. For example, I will encourage you to be sure to take both Math 71 and 81, Math 63 and 73 as well as Math 43 and several other advanced courses (depending on your interests). These are all great courses, so even if you don't end up going to graduate school in mathematics, you'll have a great time.