# Almost fixed

Author: mathforces
Problem has been solved: 10 times

Русский язык | English Language

We call a function $f: \ \{1,2,3,...,n\} \to \{1,2,...,n\}$ almost fixed if it is one-to-one and for any pair $(x, y )$ if the number $x$ is divisible by $y$, then $f (x)$ is divisible by $f (y)$. Find the number of almost fixed functions for $n = 40$. If such functions do not exist, enter 999999.