New representations for all sporadic Apéry-like sequences, with applications to congruences

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1. Verfasser: Gorodetsky, Ofir
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Veröffentlicht: 2021
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author Gorodetsky, Ofir
author_facet Gorodetsky, Ofir
contents We find new representations, in terms of constant terms of powers of Laurent polynomials, for all the 15 sporadic Ap{é}ry-like sequences discovered by Zagier, Almkvist-Zudilin and Cooper. The new representations lead to binomial expressions for the sequences, which, as opposed to previous expressions, do not involve powers of 3 or 8. We use these to establish the supercongruence $B_{np^k} \equiv B_{np^{k-1}} \bmod p^{2k}$ for all primes $p \ge 3$ and integers $n,k \ge 1$, where $B_n$ is a sequence discovered by Zagier, known as Sequence $\mathbf{B}$. Additionally, for 14 of the 15 sequences, the Newton polytopes of the Laurent polynomials contain the origin as their only interior integral point. This property allows us to prove that these sequences satisfy a strong form of the Lucas congruences, extending work of Malik and Straub. Moreover, we obtain lower bounds on the $p$-adic valuation of these sequences via recent work of Delaygue.
format Preprint
id arxiv_https___arxiv_org_abs_2102_11839
institution arXiv
publishDate 2021
record_format arxiv
spellingShingle New representations for all sporadic Apéry-like sequences, with applications to congruences
Gorodetsky, Ofir
Number Theory
We find new representations, in terms of constant terms of powers of Laurent polynomials, for all the 15 sporadic Ap{é}ry-like sequences discovered by Zagier, Almkvist-Zudilin and Cooper. The new representations lead to binomial expressions for the sequences, which, as opposed to previous expressions, do not involve powers of 3 or 8. We use these to establish the supercongruence $B_{np^k} \equiv B_{np^{k-1}} \bmod p^{2k}$ for all primes $p \ge 3$ and integers $n,k \ge 1$, where $B_n$ is a sequence discovered by Zagier, known as Sequence $\mathbf{B}$. Additionally, for 14 of the 15 sequences, the Newton polytopes of the Laurent polynomials contain the origin as their only interior integral point. This property allows us to prove that these sequences satisfy a strong form of the Lucas congruences, extending work of Malik and Straub. Moreover, we obtain lower bounds on the $p$-adic valuation of these sequences via recent work of Delaygue.
title New representations for all sporadic Apéry-like sequences, with applications to congruences
topic Number Theory
url https://arxiv.org/abs/2102.11839