Question 102
How many functions $f:\{1,2,3,4,5\} \rightarrow \{1,2,3,4,5\}$ satisfy $f(f(x))=f(x)$ for all $x \in \{1,2,3,4,5\}$?
MathNet 2009-part-05 — 172 problems (EN–VI) Question 102
Math Olympiad Vault · MathNet 2009-part-05 — 172 problems (EN–VI)