Should I ask a letter of recommendation from a prof who I rarely see? I'm applying to grad school this fall for math PhD programs and I need to figure out who to ask for letters of rec. I'm doing a summer reading course which is technically under a professor, but since he is really busy it's actually under a grad student. I've seen the professor only once or twice for paperwork, but I mainly work with the grad student. At the end of the course, should I ask the grad student to write about me and give it to the professor for him to write me a letter of rec? Or is this a bad idea?
A question you have to consider is - does the Professor know enough about your work, work ethic, attitude etc to be able to write a strong and meaningful reference for you.  A 'vague' and 'form-letter' type of reference could potentially harm your application, if it is the main reference you use.

Having said that, it would not hurt to ask and obtain a reference (if the Professor is comfortable doing so) to add to your portfolio.