If a graph has q2 + q + 1 vertices (q > 13), e edges and no 4-cycles then e ≤ 1/2q(q + 1)2. Equality holds for graphs obtained from finite projective planes with polarities. This partly answers a question of Erdos from the 1930's.
ASJC Scopus subject areas
- Theoretical Computer Science
- Discrete Mathematics and Combinatorics
- Computational Theory and Mathematics