The biggest number

I have given you all an index card. You have one minute to write down the biggest number that you can (barring infinity) using any mathematical function that you know (addition, subtraction, exponentation, ackermann, Knuth's up arrow, etc). Go.

>>32
Ah, sorry, brain fart. We were talking about this in /g/.

Kleene published a paper called "Recursive predicates and quantifiers" in 1943, which was about some related concepts. His paper was then used in book called "The Undecidable" in 1965 which then used it to demonstrate nested Busy Beavers.

... eh, supposedly. I haven't actually read either. The whole thing is pointless mathematical masturbation, anyway. Who gives a shit?