Godel number   You just edited that article  Unfortunately the definition is completely screwy it makes no sense to say that a function from S to N is computable if elements of S have not already been assigned Godel numbers  And a computable function cannot output random elements unless they have been assigned Godel numbers  So neither the function f nor its inverse could possibly be computable if S is anything other than the natural numbers   If you are interested in fixing the article please feel free nobody else has stepped up and I am putting it off There is already some discussion on the talk page in the section Definition Im writing because minor changes you make might get lost if and when the article is rewritten and that would be a waste of your time