Divisibility and sequence properties of σ⁺ and φ⁺

Inspired by Lehmer’s and Deaconescu’s conjectures, as well as various analogue problems concerning Euler’s totient function φ(n), Schemmel’s totient function S₂(n), Jordan totient function Jₖ, and the unitary totient function φ*(n), we investigate analogous divisibility problems involving the functions σ(n), σ⁺(n), and φ⁺(n). Further, we establish some interesting properties of the sequences {σ⁺(n)}ₙ₌₁^∞ and {φ⁺(n)}ₙ₌₁^∞, in particular, we prove that each of these sequences contains infinitely many arithmetic progressions of length 3.

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Publication Details

Journal
SHILAP Revista de lepidopterología
Published
2025-12-01
DOI
https://doi.org/10.7546/nntdm.2025.31.4.899-907
Primary Topic
Advanced Mathematical Identities
Type
article
Field-Weighted Citation Impact
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article

Divisibility and sequence properties of σ⁺ and φ⁺

Sagar Mandal
SHILAP Revista de lepidopterología
Advanced Mathematical Identities
article

Divisibility and sequence properties of σ⁺ and φ⁺

Sagar Mandal
article en

Abstract

Inspired by Lehmer’s and Deaconescu’s conjectures, as well as various analogue problems concerning Euler’s totient function φ(n), Schemmel’s totient function S₂(n), Jordan totient function Jₖ, and the unitary totient function φ*(n), we investigate analogous divisibility problems involving the functions σ(n), σ⁺(n), and φ⁺(n). Further, we establish some interesting properties of the sequences {σ⁺(n)}ₙ₌₁^∞ and {φ⁺(n)}ₙ₌₁^∞, in particular, we prove that each of these sequences contains infinitely many arithmetic progressions of length 3.

SHILAP Revista de lepidopterología
Indian Institute of Technology Ropar (IN)
Openalex Percentile: Top 12%
Advanced Mathematical Identities
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