English

On coprimality of consecutive elements in certain sequences

Number Theory 2025-06-27 v1

Abstract

The study of finding blocks of primes in certain arithmetic sequences is one of the classical problems in number theory. It is also very interesting to study blocks of consecutive elements in such sequences that are pairwise coprime. In this context, we show that if ff is a twice continuously differentiable real-valued function on [1,)[1, \infty) such that f(x)0f''(x) \to 0 as xx \to \infty and lim supxf(x)=\limsup_{x \to \infty} f'(x) = \infty, then there exist arbitrarily long blocks of pairwise coprime consecutive elements in the sequence (f(n))n(\lfloor f(n) \rfloor)_n. This result refines the qualitative part of a recent result by the first author, Drmota and M\"{u}llner. We also prove that there exists a subset AN\mathcal{A} \subseteq \mathbb{N} having upper Banach density one such that for any two distinct integers m,nAm, n \in \mathcal{A}, the integers f(m)\lfloor f(m) \rfloor and f(n)\lfloor f(n) \rfloor are pairwise coprime. Further, we show that there exist arbitrarily long blocks of consecutive elements in the sequence (f(n))n(\lfloor f(n) \rfloor)_n such that no two of them are pairwise coprime.

Keywords

Cite

@article{arxiv.2506.20948,
  title  = {On coprimality of consecutive elements in certain sequences},
  author = {Jean-Marc Deshouillers and Sunil Naik},
  journal= {arXiv preprint arXiv:2506.20948},
  year   = {2025}
}
R2 v1 2026-07-01T03:33:55.445Z