You're probably better off using math notation software (like LaTeX, MathMagic, or MathType) and outputting to a PDF.
Use that PDF directly in AE, or open with Photoshop or Illustrator to chop up into layers.
At the link in Daftly's reply, the Mathematical Pi font is a good one, but a couple other thoughts...
- The standard in the world of math publishing is, or will soon become, the STIX family of fonts. If you look at the bottom of their page and see the 6 huge organizations who are behind these fonts, you'll see why.
- Any decent Unicode font (whether or not it has Unicode in its name) will have a full complement of Greek symbols.
- What a Unicode font won't have are characters that stretch, like the parentheses in your example. For that, you'll need "math notation software" such as the ones Navarro mentioned. Either that, or you'll be doing a lot of manual editing in Illustrator.
- The style guide for whoever you're submitting your work to, whether it's your university to which you'll submit your work or a corporation you work for, will likely have specifications for typesetting, and may specify a particular font. I've worked with a corporation that specified Palatino for publication, which I personally like as a font, but it's nigh impossible to typeset middle-level to advanced math in Palatino. Hopefully you can find some compromise.
I plan to be extruding these in 3d..... matt