A derangement of a set $A$ is a bijection from $A$ to itself with no fixed points. Is it the case that every infinite set has a derangement?
2026-02-23 04:43:14.1771821794
Does every set have a derangement?
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Assuming all the elements are different, the bijections of a set of size $n$ are equivalent to permutations: label the elements $1,2,\ldots,n$. So there are as many derangements for a set of size $n$ as there are for the numbers $1,2\ldots,n$