In this note, we show that for n = 4N + 3, N N 0 , the expo- nential Diophantine equation nx + 24y = z2 has exactly two solutions if n + 1 or equivalently N + 1 is an square. When N + 1 = m2, the solutions are given by (0, 1, 5) and (1, 0, 2m). Otherwise it has a unique solution (0, 1, 5) in non-negative integers. Finally, we leave an open problem to explore.