On differences of two harmonic numbers

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Hauptverfasser: Lim, Jeck, Steinerberger, Stefan
Format: Preprint
Veröffentlicht: 2024
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author Lim, Jeck
Steinerberger, Stefan
author_facet Lim, Jeck
Steinerberger, Stefan
contents We prove that the existence of infinitely many $(m_k, n_k) \in \mathbb{N}^2$ such that the difference of harmonic numbers $H_{m_k} - H_{n_k}$ approximates 1 well $$ \lim_{k \rightarrow \infty} \left| \sum_{\ell = n}^{m_k} \frac{1}{\ell} - 1 \right|\cdot n_k^2 = 0.$$ This answers a question of Erdős and Graham. The construction uses asymptotics for harmonic numbers, the precise nature of the continued fraction expansion of $e$ and a suitable rescaling of a subsequence of convergents. We also prove a quantitative rate by appealing to techniques of Heilbronn, Danicic, Harman, Hooley and others regarding $\min_{1 \leq n \leq N} \min_{m \in \mathbb{N}}\| n^2 θ- m\|$.
format Preprint
id arxiv_https___arxiv_org_abs_2405_11354
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle On differences of two harmonic numbers
Lim, Jeck
Steinerberger, Stefan
Combinatorics
We prove that the existence of infinitely many $(m_k, n_k) \in \mathbb{N}^2$ such that the difference of harmonic numbers $H_{m_k} - H_{n_k}$ approximates 1 well $$ \lim_{k \rightarrow \infty} \left| \sum_{\ell = n}^{m_k} \frac{1}{\ell} - 1 \right|\cdot n_k^2 = 0.$$ This answers a question of Erdős and Graham. The construction uses asymptotics for harmonic numbers, the precise nature of the continued fraction expansion of $e$ and a suitable rescaling of a subsequence of convergents. We also prove a quantitative rate by appealing to techniques of Heilbronn, Danicic, Harman, Hooley and others regarding $\min_{1 \leq n \leq N} \min_{m \in \mathbb{N}}\| n^2 θ- m\|$.
title On differences of two harmonic numbers
topic Combinatorics
url https://arxiv.org/abs/2405.11354