Hey Rachel! Upper-level artsci here. Artsci 1D06 is equivalent to Math 1A03/1AA3. I'm guessing the Math department just forgot to include it in the list of requirements. If you look at the course calendar, anywhere 1A03/1AA3 is a prerequisite, so is 1D06. I'm also considering a Math minor, and I've never had a problem.
That said, at some point you'll want to point the error out to the math department so that they can fix it (I suppose I will too!). It shouldn't be a big deal, the soon-to-be math undergrad chair (Dr. Lovric) used to teach Artsci 1D06.
1D06 is basically the same course, just more awesome because it's with artscis. Plus there's some bonus lectures that are super interesting.
Hope that helps!