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 A188983 #22 Mar 17 2023 09:55:12
%S A188983 1,3,5,9,119,597,2035,4449,239,56403,341525,1315911,3455641,3627003,
%T A188983 23161315,186118929,815616479,2474152797,4241902555,6712571031,
%U A188983 95420159401,485257533003,1671083125805,3718150825791,584824319281,44827014819597,276564805068235,1076637637754649,2864483360640839,3190610873034597,18094618450123325
%N A188983 Odd numbers y such that x^2 + y^2 = 13^n with x and y coprime.
%C A188983 The x values are in A188982.
%C A188983 This is also the absolute value of the real part of (3+2i)^n, where i = sqrt(-1). The signed version is A121622.
%H A188983 Vincenzo Librandi, <a href="/A188983/b188983.txt">Table of n, a(n) for n = 0..183</a>
%t A188983 Table[s = Select[PowersRepresentations[13^n, 2, 2], CoprimeQ @@ # &, 1][[1]]; Select[s, OddQ][[1]], {n, 0, 30}]
%o A188983 (Magma) [Integers()!Abs(Real((3+2*Sqrt(-1))^n)): n in [0..30]]; // _Bruno Berselli_, May 26 2011
%Y A188983 Cf. A121622, A158936, A188982.
%K A188983 nonn
%O A188983 0,2
%A A188983 _T. D. Noe_, Apr 14 2011