Counting independent sets in Riordan graphs

Cheon, Gi-Sang and Jung, Ji-Hwan and Kang, Bumtle and Kim, Hana and Kim, Suh-Ryung and Kitaev, Sergey and Mojallal, Seyed Ahmad (2020) Counting independent sets in Riordan graphs. Discrete Mathematics, 343 (11). 112043. ISSN 0012-365X (

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The notion of a Riordan graph was introduced recently, and it is a far-reaching generalization of the well-known Pascal graphs and Toeplitz graphs. However, apart from a certain subclass of Toeplitz graphs, nothing was known on independent sets in Riordan graphs. In this paper, we give exact enumeration and lower and upper bounds for the number of independent sets for various classes of Riordan graphs. Remarkably, we offer a variety of methods to solve the problems that range from the structural decomposition theorem to methods in combinatorics on words. Some of our results are valid for any graph.