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2026/108/1-2 (4) — DOI: 10.5486/PMD.2026.10182 — pp. 75-85

The extendibility of the parametric $D(-1)$-triples

Authors: Mirela Jukić Bokun Orcid.org link for Mirela Jukić Bokun and Ivan Soldo Orcid.org link for Ivan Soldo

Abstract:

Let $N$ be a positive integer such that $4N^2+1=q$, where $q$ is a prime. In this paper, we prove that the Diophantine $D(-1)$-triple of the form $\{1,4N^2+1,1-N\}$ cannot be extended to a quadruple in the ring $\mathbb{Z}[\sqrt{-N}]$, with a non-square integer $N>2$. If $N>2$ is a square, then $4N^2+1$ is not a prime, and the set $\{1,4N^2+1,1-N,1+N\}$ is a $D(-1)$-quadruple in the ring $\mathbb{Z}[\sqrt{-N}]$, thus also in the ring of the Gaussian integers as well.

Keywords: Diophantine $m$-tuple, quadratic field, Pellian equation, linear form in logarithms

Mathematics Subject Classification: 11D09, 11R11, 11J86