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 A254228 #7 Jun 13 2015 00:55:22 %S A254228 1,41,185,13105,59473,4219673,19150025,1358721505,6166248481, %T A254228 437504104841,1985512860761,140874963037201,639328974916465, %U A254228 45361300593873785,205861944410240873,14606197916264321473,66286906771122644545,4703150367736517640425 %N A254228 Indices of heptagonal numbers (A000566) which are also centered square numbers (A001844). %C A254228 Also positive integers x in the solutions to 5*x^2 - 4*y^2 - 3*x + 4*y - 2 = 0, the corresponding values of y being A254229. %H A254228 Colin Barker, <a href="/A254228/b254228.txt">Table of n, a(n) for n = 1..797</a> %H A254228 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,322,-322,-1,1). %F A254228 a(n) = a(n-1)+322*a(n-2)-322*a(n-3)-a(n-4)+a(n-5). %F A254228 G.f.: -x*(x^4+40*x^3-178*x^2+40*x+1) / ((x-1)*(x^2-18*x+1)*(x^2+18*x+1)). %e A254228 41 is in the sequence because the 41st heptagonal number is 4141, which is also the 46th centered square number. %o A254228 (PARI) Vec(-x*(x^4+40*x^3-178*x^2+40*x+1)/((x-1)*(x^2-18*x+1)*(x^2+18*x+1)) + O(x^100)) %Y A254228 Cf. A000566, A001844, A254229, A254230. %K A254228 nonn,easy %O A254228 1,2 %A A254228 _Colin Barker_, Jan 27 2015