Directed Graphs from Exact Covering Systems
Dana Neidmann
Department of Mathematics
University of Illinois at Urbana-Champaign
Urbana, IL 61801
USA
Abstract:
Given an exact covering system S = {ai (mod
di) : 1 ≤ i ≤ r}, we introduce
the corresponding exact covering system digraph (ECSD) GS
= G(d1n+a1, ..., drn+ar).
The vertices of GS are the integers and the edges are (n,
din + ai)
for each n ∈ Z and
for each congruence in the covering system. We study the structure of
these directed graphs, which have finitely many components, one cycle per
component, as well as indegree 1 and outdegree r at each vertex. We
also explore the link between ECSDs that have a single component and
non-standard digital representations of integers.
Full version: pdf,
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(Concerned with sequences
A002487
A110081.)
Received March 2 2021;
revised versions received November 3 2021; January 24 2022; January 31 2022.
Published in Journal of Integer Sequences,
February 1 2022.
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