Pell or Pell-Lucas numbers as concatenations of two repdigits in base $b$

Kouessi Norbert Adedji, Alan Filipin, Salah Eddine Rihane, Alain Togbe

Published 2022-10-18Version 1

Let $b$ be a positive integer such that $2 \leq b \leq 10$. In this study, we find all Pell or Pell-Lucas numbers as concatenations of two repdigits in base $b$. As a corollary, it is show that the largest Pell or Pell-Lucas numbers which can be expressible as a concatenations of two repdigits in base $b$ are $P_{11} = 5741$ and $Q_5 = 82$, respectively.