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MathNet 2019-part-01 — 184 problems (EN–VI) Question 85

Math Olympiad Vault · MathNet 2019-part-01 — 184 problems (EN–VI)

Question 85

For a positive integer $n$, consider all nonincreasing functions $f: \{1, \dots, n\} \to \{1, \dots, n\}$. Some of them have a fixed-point ($c = f(c)$), some don't have. Which are more numerous? Evaluate the difference between the sizes of the two sets of functions.