Tetration

Tetration is an operation which succeeds Exponentiation in the hierarchy of hyper-operators. It is often denoted by two double arrows, ($$a\uparrow \uparrow b$$), where a is the base and b is the tetrational exponent, or the number of times a is stacked upon itself in a exponential stack.

Properties
Tetration has an equal growth rate equal to $$f_{3}(n)$$ in the fast-growing hierarchy.