Journal of Integer Sequences, Vol. 28 (2025), Article 25.3.3

On Reduced Unicellular Hypermonopoles


Robert Cori
Labri, Université Bordeaux 1
33405 Talence Cedex
France

Gábor Hetyei
Department of Mathematics and Statistics
UNC Charlotte
Charlotte NC 28223-0001
USA

Abstract:

The problem of counting unicellular hypermonopoles by the number of their hyperedges is equivalent to describing the cycle length distribution of a product of two cyclic permutations, first solved by Zagier. The solution of this problem has also been used in the study of the cycle graph model of Bafna and Pevzner, and of related models in mathematical biology. In this paper we develop a method to compute the finite number of reduced unicellular hypermonopoles of a given genus. The problem of representing any hypermap as a drawing is known to be simplifiable to solving the same problem for reduced unicellular hypermonopoles. We also outline a correspondence between our hypermap model, the cycle graph model of Bafna and Pevzner, and the polygon gluing model of Alexeev and Zograf. Reduced unicellular hypermonopoles correspond to reduced objects in the other models as well, and the notion of genus is the same.


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(Concerned with sequences A164652 A371665.)


Received April 24 2024; revised versions received December 14 2024; April 1 2025; April 2 2025. Published in Journal of Integer Sequences, April 15 2025.


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