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 A229848 #11 Oct 09 2013 03:11:19
%S A229848 1,4,7,9,13,16,19,25,28,31,36,37,43,49,52,61,63,64,67,76,79,81,91,100,
%T A229848 103,109,112,117,121,124,127,139,144,148,151,157,163,169,171,172,175,
%U A229848 181,193,196,199,208,211,217,223,225,229,244,247,252,256,268,271
%N A229848 Values of n such that the equation x^2 - 3*n*y^2 = n has integer solutions.
%e A229848 37 appears in the sequence because the equation x^2 - 111*y^2 = 37 has integer solutions.
%t A229848 Select[Range[300],Length[FullSimplify[Solve[x^2-3*#*y^2==#,{x,y},Integers]/.C[1]->1]]>0&] (* _Vaclav Kotesovec_, Oct 08 2013 *)
%Y A229848 Cf. A172000, A227939
%K A229848 nonn
%O A229848 1,2
%A A229848 _Colin Barker_, Oct 07 2013