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 A051215 #9 May 14 2017 22:48:21
%S A051215 0,1,3,4,7,12,15,16,28,31,39,48,55,60,63,64,87,112,124,127,135,156,
%T A051215 175,183,192,207,220,231,240,247,252,255,256,295,348,375,399,448,495,
%U A051215 496,508,511,540,583,615,624,663,700,732,735,759,768,799,828,847,855,880
%N A051215 Numbers of the form 4^x-y^2 >= 0.
%t A051215 max = 1000; Clear[f]; f[m_] := f[m] = Select[Table[4^x - y^2, {x, 0, m}, {y, 0, Ceiling[4^(x/2)]}] // Flatten // Union, 0 <= # <= max &]; f[1]; f[m = 2]; While[f[m] != f[m - 1], m++]; Print["m = ", m]; A051215 = f[m] (* _Jean-François Alcover_, May 14 2017 *)
%K A051215 nonn
%O A051215 1,3
%A A051215 _David W. Wilson_