MathDB
maximum 4-cycles in Cn digraph

Source: Mongolia 1999 Teachers secondary level P2

May 6, 2021
combinatorics

Problem Statement

Any two vertices A,BA,B of a regular nn-gon are connected by an oriented segment (i.e. either ABA\to B or BAB\to A). Find the maximum possible number of quadruples (A,B,C,D)(A,B,C,D) of vertices such that ABCDAA\to B\to C\to D\to A.