Enumarative combinatorics

Double counting
Tripple counting

Binominalkoeffizent
Binomischer Lehrsatz
Pascaltriangle
combinatorial identities
multinomial coeffcients
multinomial therom

Vandermodes identity

Random proof

Proof of Lucas

Stirling Numbers
Falling Factorial
Bell numbers
Ordered Bell Numbers

Inklusion-Exklusion
Counting sujektions
Eulers phi-Funktion

Catalan Numbers