Question 77
Find all injection functions $f: \mathbb{N} \rightarrow \mathbb{N}$ such that
$$
f(f(n)) \leq \frac{n+f(n)}{2}, \quad \forall n \in \mathbb{N}.
$$
$$
f(f(n)) \leq \frac{n+f(n)}{2}, \quad \forall n \in \mathbb{N}.
$$
MathNet 2008-part-03 — 165 problems (EN–VI) Question 77
Math Olympiad Vault · MathNet 2008-part-03 — 165 problems (EN–VI)