Sums of three Fibonacci numbers as concatenations of three repdigits in base $b$
Passimzouwé Dagou, Pagdame Tiebekabe, Kouèssi Norbert Adédji, Kokou Tchariè
Abstract
In this paper, we investigate sums of three Fibonacci numbers that can be expressed as concatenations of three repdigits in base $b$, where $b\ge 2$ is an integer. We prove that for bases $2\le b\le 10$, only finitely many such sums exist, and we determine all of them explicitly. Among these solutions, the largest occurs for $b=4$ and is given by $$ F_{42}+F_{29}+F_{20}=268435290=\overline{33333333331122}_4. $$
