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%I #18 Dec 22 2020 18:29:21
%S 1,8,47,161,404,495,2908,31679,203996,905768,2529647,4839120,4291039,
%T 116593352,859799153,4896306240,14978251196,35359140465,28242853388,
%U 375162560801,3481428994004,21473668418415,85367854683953,228866364286560
%N Values of x such that x^2 + y^2 = 17^n with x and y coprime and 0 < x < y.
%C The corresponding y-values are in A230623.
%H Vincenzo Librandi, <a href="/A230622/b230622.txt">Table of n, a(n) for n = 1..200</a>
%H Chris Busenhart, Lorenz Halbeisen, Norbert Hungerbühler, Oliver Riesen, <a href="https://people.math.ethz.ch/~halorenz/publications/pdf/Miniatur.pdf">On primitive solutions of the Diophantine equation x^2+ y^2= M</a>, Eidgenössische Technische Hochschule (ETH Zürich, Switzerland, 2020).
%e a(2)=8 because 8^2+15^2=289=17^2.
%t Table[Select[PowersRepresentations[17^n, 2, 2], CoprimeQ@@#&][[1, 1]], {n, 1, 40}] (* _Vincenzo Librandi_, Mar 02 2014 *)
%Y Cf. A001026, A188948, A230623.
%K nonn
%O 1,2
%A _Colin Barker_, Oct 26 2013