Mini-cours introduction aux actions de groupes par le dénombrement

(Rebroadcast) A short introduction that I hope will convince you of the very practical usefulness of group actions. We'll cover: the shepherd's lemma and the class formula. But above all, many concrete examples of their use in combinatorics and algebraic combinatorics. 00:00 The shepherd's lemma and axiomatization 06:23 Symmetric group and natural action 13:21 Linear group and natural action 23:03 Counting diagonalizable matrices 27:18 Generating series in counting 42:13 Counting matrices of rank r