Factorials, binomial coefficients.
Binomial series identity and resulting relations of binomial coefficients.
Combinatoric operations (summation rule, product rule, permutation, combination).
Inclusion and exclusion principle.
Dirichlet's principle.
Transition from combinatorics to probability.
The secondary school knowledge of combinatoric operations (variation, combination, permutation) is revised and deepened. Transition from combinatorics to probability.