New posts in Derangements

Why is $!n\pmod{n+k}$ a multiple of $k+1$ so often?

$10$ letters are placed in $10$ addressed envelopes. Find the number of ways such that at most three letters are not in correct envelopes

What's the probability that a given permutation has exactly $k$ fixed points.

Why does the expansion of $e^x$ appear to arise in the formula for derangement of $n$ things $D_{n}=n!\sum_{k=0}^n \frac{(-1)^k}{k!}$

A question on Derangement Combinatorics

Placing $5$ pieces on a $5\times5$ grid with no main diagonal

Prove: Number of derangement is odd if and only if number of items is even .

Derangement of $n$ elements

Derangement problem!

Exponential Generating Function For Derangements