Lecture 11 - DERANGEMENT permutation and combination// Combinatorics Discrete Math

We'll learn about how to count derangement permutations and combinations. A derangement is a list of numbers where the number j is never in the jth position.

0:00 Introduction
0:10 Definition of a derangements
0:32 Example of a derangement
1:03 Counting derangements using inclusion exclusion
6:40 Formula for number of derangements