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 A237255 #11 Jun 13 2015 00:54:58 %S A237255 2,3,7,13,33,62,158,297,757,1423,3627,6818,17378,32667,83263,156517, %T A237255 398937,749918,1911422,3593073,9158173,17215447,43879443,82484162, %U A237255 210239042,395205363,1007315767,1893542653,4826339793,9072507902,23124383198,43468996857 %N A237255 Values of x in the solutions to x^2 - 5xy + y^2 + 17 = 0, where 0 < x < y. %C A237255 The corresponding values of y are given by a(n+2). %H A237255 Colin Barker, <a href="/A237255/b237255.txt">Table of n, a(n) for n = 1..1000</a> %H A237255 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,5,0,-1). %F A237255 a(n) = 5*a(n-2)-a(n-4). %F A237255 G.f.: -x*(x-1)*(x+2)*(2*x+1) / (x^4-5*x^2+1). %e A237255 3 is in the sequence because (x, y) = (3, 13) is a solution to x^2 - 5xy + y^2 + 17 = 0. %o A237255 (PARI) Vec(-x*(x-1)*(x+2)*(2*x+1)/(x^4-5*x^2+1) + O(x^100)) %Y A237255 Cf. A004253, A237254. %K A237255 nonn,easy %O A237255 1,1 %A A237255 _Colin Barker_, Feb 05 2014