Suppose $f$ and $g$ are functions from $\mathbb N^+$ to itself. I want to consider the function $f^g$, where $f^g(n) = f \circ \dots \circ f(n)$, where composition is done $g(n)$-many times. Note that if $f$ and $g$ are monotonic increasing then so is $f^g$. Is there a name for this operation, or something similar?