Question 134
Compute the number of functions $f:\{1,2, \ldots, 9\} \rightarrow \{1,2, \ldots, 9\}$ which satisfy $f(f(f(f(f(x))))) = x$ for each $x \in \{1,2, \ldots, 9\}$.
MathNet 2017-part-07 — 172 problems (EN–VI) Question 134
Math Olympiad Vault · MathNet 2017-part-07 — 172 problems (EN–VI)