Interesting, I found <a href="http://en.wikipedia.org/wiki/Knuth%27s_up-arrow_notation" rel="nofollow">http://en.wikipedia.org/wiki/Knuth%27s_up-arrow_notation</a> to be more interesting though as extending addition-multiplication-exponentiation-... wasn't something I'd really looked at before.
Same subject, more "folksy" write-up, no comment, more entertaining.<p><a href="http://news.ycombinator.com/item?id=1321659" rel="nofollow">http://news.ycombinator.com/item?id=1321659</a>