Some Innovations in Section “Combinatorics” of Discrete Mathematics Course

In this paper, we propose some innovations in the presentation of some issues of the discrete mathematics course. We propose a proof of the inclusion-exclusion formula using the algebraic essence of this formula. For this, the concept of a “foliated” set is introduced, which generalizes the concept of a multiset. In addition, for some basic combinatorial numbers, proofs of formulas for their calculation by natural combinatorial reasoning are proposed.