## On the power values of the sum of three squares in arithmetic progression

Mathematical Communications, vol.27, no.2, pp.137-150, 2022 (SCI-Expanded)  • Publication Type: Article / Article
• Volume: 27 Issue: 2
• Publication Date: 2022
• Journal Name: Mathematical Communications
• Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, zbMATH, Directory of Open Access Journals
• Page Numbers: pp.137-150
• Keywords: polynomial Diophantine equation, power sums, primitive divisors of Lehmer sequences, Baker's method, PERFECT POWERS, PRIMITIVE DIVISORS, EQUATION (X, LUCAS
• Bursa Uludag University Affiliated: Yes

#### Abstract

© 2022 Department of Mathematics, University of Osijek.In this paper, using a deep result on the existence of primitive divisors of Lehmer numbers due to Y. Bilu, G. Hanrot and P. M. Voutier, we first give an explicit formula for all positive integer solutions of the Diophantine equation (x−d)2 +x2 +(x+d)2 = yn (*), when n is an odd prime and d = pr, p > 3, a prime. So this improves the results of the papers of A. Koutsianas and V. Patel  and A. Koutsianas . Secondly, under the assumption of our first result, we prove that (*) has at most one solution (x, y). Next, for a general d, we prove the following two results: (i) if every odd prime divisor q of d satisfies q ≢ ±1 (mod 2n), then (*) has only the solution (x, y, d, n) = (21, 11, 2, 3), and (ii) if n > 228000 and d > 8√2, then all solutions (x, y) of (*) satisfy yn < 23/2 d3 .