Pell and Pell-Lucas numbers as difference of two repdigits

Bilizimbeye Edjeou, Bernadette Faye

Let $\{P_n{\}}_{n\ge 0}$ be the sequence of Pell numbers defined by $P_0=0$, $P_1=1$ and $P_{n+2}=2P_{n+1}+P_n$ for all $n\ge 0$ and let $\{Q_n{\}}_{n\ge 0}$ be its…