Journal of Integer Sequences, Vol. 29 (2026), Article 26.3.8

A Note on Non-Integrality of the (k, l)-Göbel Sequences


Yuh Kobayashi
Faculty of Information Design
Heisei International University
Mizubuka Odateno 2000
Kazo, Saitama 347-8504
Japan

Shin-ichiro Seki
Nagahama Institute of Bio-Science and Technology
Tamura 1266
Nagahama, Shiga, 526-0829
Japan

Abstract:

The (k, l)-Göbel sequences defined by Ibstedt remain integers for the first (in some cases, many) terms, but for selected values of (k, l) computations show that the terms eventually stop being integers. It is still unresolved whether the integrality of these sequences breaks down for all k, l ≥ 2. In this article, we prove the non-integrality for a specific class of (k, l) values. Our proof is based on geometric arguments related to the distribution of quadratic residues modulo a prime.


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(Concerned with sequences A003504 A108394.)


Received December 23 2024; revised versions received June 2 2026; June 3 2026. Published in Journal of Integer Sequences, June 4 2026.


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