Megafuga-

Megafuga- is a prefix used on a number n to indicate $$^2n$$. It was invented by Stephen Houben, who asked, when hearing about the fuga- prefix, said:

"Since the ^ operation is not associative, i.e. (x^y)^z != x^(y^z), this begs the question whether Fuga(3) means (3^3)^3 = 19683 or 3^(3^3) = 7625597484987. Probably the latter, since the goal is to get big numbers...."

Houben noted, using a computer, that megafuga(4) is about $$4^{1.34 \times 10^{153}}$$, a bit larger than $$4^{10^{100}}$$, and concluded that "computing all [the] digits of megafuga(4) will never happen."