Xkcd number

The xkcd number is equal to \(A(G, G) = 2\uparrow^{G-2} (G+3) - 3\) or gag(G), where G is Graham's number and A is the Ackermann function.What xkcd MeansXKCD number 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.
It might horrify mathematicians as the caption claims, but the number is not terribly large for many googologists. Indeed, it is supposed to be easily dwarfed by other numbers rising out of mathematics such as TREE(3) or SCG(13), although the comparisons are not easily done due to the difficulty of these specific numbers. Googologists would consider this an example of a naive extension, or a tame example of a salad number (a derogatory term for an inelegant mishmash of existing numbers and functions). Since gag grows slower than \(3 \rightarrow 3 \rightarrow n\), the xkcd number is smaller than \(g_{65}\), and is therefore not much of an improvement over Graham's number. In BEAF, it is between \(\lbrace 3,66,1,2 \rbrace\) and \(\lbrace 3,67,1,2 \rbrace\) — easily beaten by corporal.
On the now-defunct xkcd forums, there is a thread titled My number is bigger! where posters compete to define the largest computable number possible.
=== Sources ===
Category:Numbers
Category:Non-powers
Category:Odd numbers
Category:Linear omega level
Category:Salad numbers
Category:Naive extensions
Category:Humor