: For the smallest index, the function is just simple addition. f0(n)=n+1f sub 0 of n equals n plus 1

Let’s assume you have found a functional FGH calculator (e.g., a custom JavaScript tool on a googology forum or a Python library like fgh.py ). Here is how you use it.

The (FGH) is a family of functions ( f_\alpha : \mathbbN \to \mathbbN ) indexed by ordinals ( \alpha ). It is a central tool in proof theory and googology (the study of large numbers) for comparing the growth rates of functions and defining enormous numbers.