User blog comment:Boboris02/MBOT/@comment-30167082-20161218151736/@comment-1605058-20161219171910

Actually, nearly any googological notation can be turned into a "the largest number describable with n symbols in system X" sort of function, many of which are computable and very strong. Example: take any of Bird's notations, and consider the well-formed expressions in this notation, with each digit counting as a separate character. You can also take e.g. Hyp cos' R function or whatever. Another batch of examples can be given by taking a fixed TM and asking for the largest output it produces on an input of length n. So I wouldn't say it is that difficult.