On Diophantine Equations Related to Narayana’s Cows Sequence and Double Factorials or Repdigits

Abstract

In this paper, we determine all the Narayana’s cows numbers that are factorials or double factorials. We also show that 88 is the only repdigit (i.e., a class of numbers that has reflectional symmetry across a vertical axis) that can be written as the product of consecutive Narayana’s cows numbers.