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2026/109/1-2 (13) — DOI: 10.5486/PMD.2026.10524 — pp. 245-263

On Diophantine equations involving intersection of Thabit and Williams numbers base $b$ and some ternary recurrent sequences

Authors: Bibhu Prasad Tripathy Orcid.org link for Bibhu Prasad Tripathy, Asutosh Satapathy Orcid.org link for  Asutosh Satapathy, Utkal Keshari Dutta Orcid.org link for  Utkal Keshari Dutta and Bijan Kumar Patel Orcid.org link for Bijan Kumar Patel

Abstract:

Let $\mathcal{P}_{n}$ be the $n$-th Padovan number, $E_{n}$ be the $n$-th Perrin number, and $N_{n}$ be the $n$-th Narayana's cows number. Let $b$ be a positive integer such that $b\geq 2$. In this paper, we study the Diophantine equations $$\mathcal{P}_{n}=(b\pm 1)\cdot b^{l}\pm 1,\qquad E_{n}=(b\pm 1)\cdot b^{l}\pm 1,\qquad \mbox{and} \qquad N_{n}=(b\pm 1)\cdot b^{l}\pm 1,$$ in non-negative integers $n$, $b$, and positive integer $l$. As a result, we determine the Padovan, Perrin and Narayana's cows numbers that are Thabit and Williams numbers base $b$. Moreover, we determine all solutions of the above equations within the range $2\leq b\leq 10$.

Keywords: Thabit numbers, Williams numbers, Padovan numbers, Perrin numbers, Narayana's cows numbers, linear forms in logarithms, reduction method

Mathematics Subject Classification: 11B39, 11D61, 11J86