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2019/94/3-4 (15) — DOI: 10.5486/PMD.2019.8433 — pp. 467-475

A generalization of Menon's identity to higher exponent

Authors: Yan Li, Daeyeoul Kim and Rui Qiao

Abstract:

In this note, we shall explicitly compute the following sum $$ \sum_{\substack{1\leq a,b_1,\dots,b_k\leq n\\\gcd(a,n)=1}}\operatorname{gcd}(a^\ell-1,b_1,\dots,b_k,n), $$ where $n\geq 1$, $k\geq 0$, $l\geq 1$ are integers. Our results extend Menon's identity and Sury's identity (i.e., $\ell=1$ in the above summation) to higher exponents. Note that in the case $k=0$, some of our results are recovered by the results of [21].

Keywords: Menon's identity, Dirichlet character, Dirichlet convolution, divisor function, Euler's totient function, Chinese remainder theorem

Mathematics Subject Classification: 11A07, 11A25