Quasi-(λ; n)-distance-balanced graphs
For every pair of vertices u and v with d(u; v) = n, Wun G v denotes the set of all vertices of G that are closer to u than to v. In this paper, we introduce quasi-(λ; n)-distance-balanced graphs and then study some properties of these graphs and present a formula to construct such graphs for arbitrarily diameter d. For n = 1, this class of graphs contains the quasi-λ-DB graphs recently introduced by Abedi et al. [Quasi-λ-distance-balanced graphs, Discrete Appl. Math. 227 (2017) 21{28]. Moreover, we will take a look at the problems arisen by Abedi et al. Some problems and conjecture are involved.
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