I've seen in college that some functions are not computable. The proof for that was the case of Halt(x,y) function.

The thing is, the proof used a very artificial (IMHO) case which is evaluating the function in it's own program number. In fact the whole idea of the Halt function is quite self-referencial...

I'd like to know if there is a more "normal" function which cannot be computed. Can someone show me a function which is non-computable but does not refer to itself?

I hope I made myself clear... if not, just comment and I'll explain. Thanks!