%I
%S 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 120,137,141,143,147,162,168,176,186,189,195,200,207,218,224,233,240,
%U 249,255,275,282,288,303,312,317,323,333,351,354,360,386,392,393,399
%N Nonnegative numbers of the form x^27^y.
%t 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] (* _JeanFrançois Alcover_, May 14 2017 *)
%K nonn
%O 1,2
%A _David W. Wilson_
