Contractions to k8
Leif Kjær Jørgensen · Journal of Graph Theory · 1994
Abstract It is proved that the maximal number of edges in a graph with n ≧ 8 vertices that is not contractible to K8 is 6n − 21, unless 5 divides n, and the only graphs with n = 5m vertices and more than 6n − 21 edges that are not contractible to K8 are the K5(2)‐cockades that have exactly 6n − 20 edges.