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!