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 A051209 #9 May 14 2017 03:00:33
%S A051209 0,2,3,8,9,15,18,24,29,32,35,42,48,51,57,63,72,74,80,93,95,98,99,114,
%T A051209 120,137,141,143,147,162,168,176,186,189,195,200,207,218,224,233,240,
%U A051209 249,255,275,282,288,303,312,317,323,333,351,354,360,386,392,393,399
%N A051209 Nonnegative numbers of the form x^2-7^y.
%t A051209 max = 400; Clear[f]; f[m_] := f[m] = Select[Table[x^2 - 7^y, {y, 0, m}, {x, Floor[7^(y/2)], Ceiling[Sqrt[7^y + max]]}] // Flatten // Union, 0 <= # <= max &]; f[1]; f[m = 2]; While[f[m] != f[m - 1], m++]; Print["m = ", m]; A051209 = f[m] (* _Jean-François Alcover_, May 14 2017 *)
%K A051209 nonn
%O A051209 1,2
%A A051209 _David W. Wilson_