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 A204765 #22 Jun 18 2017 02:25:47
%S A204765 0,217,220,717,1900,1917,4780,11661,11760,28441,68544,69121,166344,
%T A204765 400081,403444,970101,2332420,2352021,5654740,13594917,13709160,
%U A204765 32958817,79237560,79903417,192098640,461830921,465711820,1119633501,2691748444,2714367981
%N A204765 Nonnegative values x of solutions (x, y) to the Diophantine equation x^2+(x+239)^2 = y^2.
%H A204765 Vincenzo Librandi, <a href="/A204765/b204765.txt">Table of n, a(n) for n = 1..1000</a>
%H A204765 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,6,-6,0,-1,1).
%F A204765 G.f.: x^2*(119*x^5+x^4+119*x^3-497*x^2-3*x-217)/((x-1)*(x^6-6*x^3+1)). [_Colin Barker_, Aug 05 2012]
%t A204765 LinearRecurrence[{1,0,6,-6,0,-1,1}, {0,217,220,717,1900,1917,4780}, 70]
%Y A204765 Cf. A185394, A198294, A203619, A206426
%K A204765 nonn,easy
%O A204765 1,2
%A A204765 _Vladimir Joseph Stephan Orlovsky_, Feb 09 2012