[cousin_it]

Sorry, it ain't self-referential unless it draws the picture around (0, 0).

I have no idea if that's possible, though. Quines are possible in many programming languages, but the "language" of formulas without quantifiers is very limited. You can encode boolean logic, not sure about loops.

EDIT:

After some Googling, I've found a true self-referential formula: http://jtra.cz/stuff/essays/math-self-reference/index.html

Note that it involves a recursive function definition, and part of the formula is generated by a fixpoint trick. I suppose that's the simplest way to do this.

Also I really enjoyed the way he embedded a watermark into the formula, in a way that's difficult to remove if you don't know what you're doing.

[userbinator]

Quines are possible in compression algorithms too: http://research.swtch.com/zip

Combining that with a self-referential formula could conceivably lead to something like a formula that generates a compressed zipfile, whose contents are a bitmap image of the formula...