Xkcd number

The xkcd number is equal to $$A(G, G)$$ or gag(G), where G is Graham's number and A is the Ackermann function. It was invented by Randall Munroe, the creator of the popular webcomic xkcd, in the third part of strip #207, which says, "[xkcd] means calling the Ackermann function with Graham's number as the arguments just to horrify mathematicians." The number was given its name by various other bloggers.

Ironically, despite the caption, not only would this number not horrify mathematicians, but googologist's would consider this an example of a naive extension or worse yet, a tame example of a salad number (a derogatory term for a mishmash of existing numbers and functions) . The function gag(n) is much slower than G(n). Consequently, A(G,G) is somewhere in the ballpark of G(65) and is therefore not much of an improvement over Graham's Number, relatively speaking.