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Paper   IPM / M / 15371
School of Mathematics
  Title:   Some results on the independence polynomial of unicycle graphs
  Author(s):  Mohammad Reza Oboudi
  Status:   Published
  Journal: Discussiones Mathematicae Graph Theory
  Vol.:  38
  Year:  2018
  Pages:   515-524
  Supported by:  IPM
  Abstract:
Let G be a simple graph on n vertices. An independent set in a graph is a set of pairwise non-adjacent vertices. The independence polynomial of G is the polynomial I(G,x)=∑k=0n s(G,k)xk, where s(G,k) is the number of independent sets of G with size k and s(G,0)=1. A unicyclic graph is a graph containing exactly one cycle. Let Cn be the cycle on n vertices. In this paper we study the independence polynomial of unicyclic graphs. We show that among all connected unicyclic graphs G on n vertices ( except two of them), I(G,t) > I(Cn,t) for sufficiently large t. Finally for every n ≥ 3 we find all connected graphs H such that I(H,x)=I(Cn,x).


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