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 A243178 #8 Jun 20 2014 15:00:06
%S A243178 0,1,4,9,11,15,16,21,25,29,35,36,39,44,49,51,60,64,65,71,79,81,84,85,
%T A243178 91,99,100,109,116,119,121,135,140,141,144,149,151,156,165,169,176,
%U A243178 179,189,191,196,204,211,219,221,225,231,235,239,240,249,256,260,261,275,281,284,289,291,309,315,316,319,324,329,331,336,340,351,359,361,364,365,375
%N A243178 Numbers of the form x^2+xy+9y^2.
%C A243178 Discriminant -35.
%H A243178 N. J. A. Sloane et al., <a href="https://oeis.org/wiki/Binary_Quadratic_Forms_and_OEIS">Binary Quadratic Forms and OEIS</a> (Index to related sequences, programs, references)
%t A243178 ofTheFormQ[n_] := Reduce[n == x^2 + x*y + 9*y^2, {x, y}, Integers] =!= False; Select[Range[0, 400], ofTheFormQ] (* _Jean-François Alcover_, Jun 04 2014 *)
%Y A243178 Primes: A106881.
%K A243178 nonn
%O A243178 1,3
%A A243178 _N. J. A. Sloane_, Jun 02 2014