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2020/96/3-4 (4) — DOI: 10.5486/PMD.2020.8577 — pp. 315-346

Congruences involving binomial coefficients and Apéry-like numbers

Authors: Zhi-Hong Sun

Abstract:

For $n=0,1,2,\ldots$, let $W_n=\sum_{k=0}^{[n/3]}\binom{2k}k\binom{3k}k\binom n{3k}(-3)^{n-3k}$, where $[x]$ is the greatest integer not exceeding $x$. Then $\{W_n\}$ is an Apéry-like sequence. In this paper we deduce many congruences involving $\{W_n\}$, in particular, we determine $\sum_{k=0}^{p-1}\binom{2k}k\frac{W_k}{m^k}\pmod p$ for $m=-640332,-5292,-972,-108,-44,-27,-12,8,54,243$ by using binary quadratic forms, where $p>3$ is a prime. We also prove several congruences for generalized Apéry-like numbers, and pose 29 challenging conjectures on congruences involving binomial coefficients and Apéry-like numbers.

Keywords: Apéry-like numbers, binomial coefficients, congruence, binary quadratic form, Legendre polynomial, Bernoulli number

Mathematics Subject Classification: 11A07, 11A15, 11B50, 11B65, 11B68, 11E25, 11F11, 33C45, 65Q30