Realizability of Some Combinatorial Sequences

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1. Verfasser: Zhang, Geng-Rui
Format: Preprint
Veröffentlicht: 2023
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author Zhang, Geng-Rui
author_facet Zhang, Geng-Rui
contents A sequence $a=(a_n)_{n=1}^\infty$ of non-negative integers is called realizable if there is a self-map $T:X\to X$ on a set $X$ such that $a_n$ is equal to the number of periodic points of $T$ in $X$ of (not necessarily exact) period $n$, for all $n\geq1$. The sequence $a$ is called almost realizable if there exists a positive integer $m$ such that $(ma_n)_{n=1}^\infty$ is realizable. In this article, we show that certain wide classes of integer sequences are realizable, which contain many famous combinatorial sequences, such as the sequences of Apéry numbers of both kinds, central Delannoy numbers, Franel numbers, Domb numbers, Zagier numbers, and central trinomial coefficients. We also show that the sequences of Catalan numbers, Motzkin numbers, and large and small Schröder numbers are not almost realizable.
format Preprint
id arxiv_https___arxiv_org_abs_2302_09454
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Realizability of Some Combinatorial Sequences
Zhang, Geng-Rui
Number Theory
Combinatorics
Dynamical Systems
Primary 11B50, Secondary 37P35, 05A10, 11B83
A sequence $a=(a_n)_{n=1}^\infty$ of non-negative integers is called realizable if there is a self-map $T:X\to X$ on a set $X$ such that $a_n$ is equal to the number of periodic points of $T$ in $X$ of (not necessarily exact) period $n$, for all $n\geq1$. The sequence $a$ is called almost realizable if there exists a positive integer $m$ such that $(ma_n)_{n=1}^\infty$ is realizable. In this article, we show that certain wide classes of integer sequences are realizable, which contain many famous combinatorial sequences, such as the sequences of Apéry numbers of both kinds, central Delannoy numbers, Franel numbers, Domb numbers, Zagier numbers, and central trinomial coefficients. We also show that the sequences of Catalan numbers, Motzkin numbers, and large and small Schröder numbers are not almost realizable.
title Realizability of Some Combinatorial Sequences
topic Number Theory
Combinatorics
Dynamical Systems
Primary 11B50, Secondary 37P35, 05A10, 11B83
url https://arxiv.org/abs/2302.09454