Edge Covers of Caterpillars, Cycles with Pendants, and Spider Graphs
Feryal Alayont and Evan Henning
Department of Mathematics
Grand Valley State University
Allendale, MI 49401
USA
Abstract:
An edge cover of a simple graph is a subset of the edges so that each
vertex is incident with at least one edge in the subset. The edge cover
polynomial of a graph is the generating polynomial of the number of
edge covers of the graph with k edges. The number of edge covers of path
graphs form the Fibonacci sequence, while those of cycle graphs form the
Lucas numbers. In this paper, we first provide some known and new general
results on edge covers and edge cover polynomials. We then apply these
results to find the number of edge covers and the edge cover polynomials
of caterpillar graphs, cycles with pendants, and spider graphs, which are
generalizations of star graphs. The number of edge covers of all these
families can be expressed in terms of Fibonacci numbers. We generate
new sequences not in the On-Line Encyclopedia of Integer Sequences using
these edge covers and provide new combinatorial interpretations of some
known sequences.
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(Concerned with sequences
A000045
A000225
A003946
A005057
A011973
A013609
A024023
A056570
A066258
A074909
A123521
A190543
A272866
A350473
A358917
A358934.)
Received December 26 2022; revised versions received December 31 2022; October 14 2023; November 12 2023.
Published in Journal of Integer Sequences,
November 16 2023.
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