English

On certain $D(9)$ and $D(64)$ Diophantine triples

Number Theory 2026-07-28 v1

Abstract

A set of mm distinct positive integers {a1,am}\{a_{1},\dots a_{m}\} is called a D(q)D(q)-mm-tuple for nonzero integer qq if the product of any two increased by qq, aiaj+qa_{i}a_{j}+q, iji\neq j is a perfect square. Due to certain properties of the sequence, there are many D(q)D(q)-Diophantine triples related to the Fibonacci numbers. A result of Ba\'{c}i\'{c} and Filipin characterizes the solutions of Pellian equations that correspond to D(4)D(4)-Diophantine triples of a certain form. We generalize this result in order to characterize the solutions of Pellian equations that correspond to D(l2)D(l^2)-Diophantine triples satisfying particular divisibility conditions. % Subsequently, we employ this result and bounds on linear forms in logarithms of algebraic numbers in order to classify all D(9)D(9) and D(64)D(64)-Diophantine triples of the form {F2n+8,9F2n+4,Fk}\{F_{2n+8},9F_{2n+4},F_{k}\} and {F2n+12,16F2n+6,Fk}\{F_{2n+12},16F_{2n+6},F_{k}\}, where FiF_{i} denotes the iith Fibonacci number.

Cite

@article{arxiv.2607.25168,
  title  = {On certain $D(9)$ and $D(64)$ Diophantine triples},
  author = {Benjamin Earp-Lynch and Simon Earp-Lynch and Omar Kihel},
  journal= {arXiv preprint arXiv:2607.25168},
  year   = {2026}
}

Comments

28 pages. This is a pre-print of an article published in Acta Mathematica Hungarica. The final published version is available at https://doi.org/10.1007/s10474-020-01061-2