Fibonacci Numbers and Vieta Jumping for a Rational Diophantine Equation

Fuente: arXiv
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Main Authors: Miller, Steven J., Nikolakopoulos, Dimitrios, Srinivasan, Anitha
Format: Preprint
Published: 2026
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author Miller, Steven J.
Nikolakopoulos, Dimitrios
Srinivasan, Anitha
author_facet Miller, Steven J.
Nikolakopoulos, Dimitrios
Srinivasan, Anitha
contents We study the Diophantine equation $\displaystyle{\tfrac{a+1}{b} + \tfrac{b+1}{a} \ = \ k}$, where $k$ is an integer. Using Vieta jumping, we completely classify all positive integer pairs $(a, \, b)$. We prove that the associated integer value $k$ can only be $3$ or $4$. The corresponding solution pairs $(a,\,b)$ are related to the classical Fibonacci numbers. As a consequence, the quantity $\frac{a+b}{\gcd(a, \,b)^2}$ takes only the values $1, \, 2, \, 3$ and $5$. This reveals an unexpected connection between a simple rational Diophantine condition, Vieta jumping, and Fibonacci numbers.
format Preprint
id arxiv_https___arxiv_org_abs_2605_19083
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Fibonacci Numbers and Vieta Jumping for a Rational Diophantine Equation
Miller, Steven J.
Nikolakopoulos, Dimitrios
Srinivasan, Anitha
Number Theory
11D68, 11D72
We study the Diophantine equation $\displaystyle{\tfrac{a+1}{b} + \tfrac{b+1}{a} \ = \ k}$, where $k$ is an integer. Using Vieta jumping, we completely classify all positive integer pairs $(a, \, b)$. We prove that the associated integer value $k$ can only be $3$ or $4$. The corresponding solution pairs $(a,\,b)$ are related to the classical Fibonacci numbers. As a consequence, the quantity $\frac{a+b}{\gcd(a, \,b)^2}$ takes only the values $1, \, 2, \, 3$ and $5$. This reveals an unexpected connection between a simple rational Diophantine condition, Vieta jumping, and Fibonacci numbers.
title Fibonacci Numbers and Vieta Jumping for a Rational Diophantine Equation
topic Number Theory
11D68, 11D72
url https://arxiv.org/abs/2605.19083