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MathNet 2011 Question 9

Math Olympiad Vault · MathNet 2011

Question 9

Let $A=\{1,2,3, \ldots, 9\}$. Find the number of bijective functions $f: A \rightarrow A$ for which there exists at least one $i \in A$ such that
$$
\left|f(i)-f^{-1}(i)\right|\gt 1
$$