This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A188948 #27 Dec 22 2020 18:29:07
%S A188948 0,2,5,9,119,122,828,4449,239,56403,145668,246046,3369960,3627003,
%T A188948 23161315,128629846,13651680,1590277918,4241902555,6712571031,
%U A188948 95420159401,107655263398,647549275812,3718150825791,584824319281,44827014819597,123471611274972,182714776311554,2701419604443960,3190610873034597,18094618450123325
%N A188948 Values of x such that x^2 + y^2 = 13^n with x and y coprime and 0 < x < y.
%C A188948 The y values are in A188949.
%H A188948 Vincenzo Librandi, <a href="/A188948/b188948.txt">Table of n, a(n) for n = 0..200</a>
%H A188948 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).
%t A188948 Table[Select[PowersRepresentations[13^n, 2, 2], CoprimeQ @@ # &][[1,1]], {n, 0, 30}]
%Y A188948 Cf. A158936, A188949.
%K A188948 nonn
%O A188948 0,2
%A A188948 _Zak Seidov_, Apr 10 2011
%E A188948 Edited by _T. D. Noe_, Apr 14 2011