Yeah, the thing is how many collinear three-point configurations to subtract. That's the real challenge. Think about it for a moment and you'll realize this is not as trivial as it may seem.

This guy understood my question

I tend to see this self-referencing problem in every non-computable function I know, and wondered if a more "mundane" function existed that satisfied this awesome property of being beyond computers' reach.

I'm sorry for my lack of appropriate language. With "artificial", I intended meaning that OK, it's true that Halt is not computable because if a program existed that computed it, and you evaluated it on its own program number, a contradiction would occur, but this seems a very special and self-referencing case. I mean, it's not a case were one would usually use Halt if it were computable. In fact (I may be wrong here, please correct me), Halt(x,y) function should be computable for many values of x and y...

I like this example but if the comment above is true, it doesn't answer my question. :D Thanks for the info, though.

@buzzard that was not the original question, but is it known to be impossible for a function to be describable and not-computable at the same time?

I was going to answer the same thing. But, in fact, BB is an interesting function. The fastest growth, and all that... Thanks for the info!

This has the same problem (IMO) that Halt(x,y) has... It is a function which refers to programs or Turing Machines to be described. In this sense, it is auto-referencial. btw: what do you mean by "H and R are in the same Turing degree." Please give a link if you don't want to explain in detail