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Diskr. Mat., 2021 Volume 33, Issue 4, Pages 61–67 (Mi dm1684)

On distance-regular graphs $\Gamma$ of diameter 3 for which $\Gamma_3$ is a triangle-free graph

A. A. Makhnevab, Venbin Guoac

a School of Mathematical Sciences, University of Science and Technology of China
b N.N. Krasovskii Institute of Mathematics and Mechanics, Ural Branch of the Russian Academy of Sciences
c Institute of Science and Technology of the Chinese Academy of Sciences

Abstract: There exist well-known distance-regular graphs $\Gamma$ of diameter 3 for which $\Gamma_3$ is a triangle-free graph. An example is given by the Johnson graph $J(8,3)$ with the intersection array $\{15,8,3;1,4,9\}$. The paper is concerned with the problem of the existence of distance-regular graphs $\Gamma$ with the intersection arrays $\{78,50,9;1,15,60\}$ and $\{174,110,18;1,30,132\}$ for which $\Gamma_3$ is a triangle-free graph.

Keywords: distance-regular graph, triangle-free graph, triple intersection numbers.

UDC: 519.172

Received: 03.04.2021

DOI: 10.4213/dm1684


 English version:
Discrete Mathematics and Applications, 2023, 33:4, 199–204


© Steklov Math. Inst. of RAS, 2025