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Numbers of the form 10^x-y^2 >= 0.
20

%I #13 May 13 2017 23:30:23

%S 0,1,6,9,10,19,36,39,51,64,75,84,91,96,99,100,144,159,199,216,271,324,

%T 375,396,424,471,516,559,591,600,639,676,711,744,775,784,804,831,856,

%U 879,900,919,936,951,964,975,984,991,996,999,1000,1164,1351,1404,1536,1719,1756,1900,1999

%N Numbers of the form 10^x-y^2 >= 0.

%t max = 2000; Clear[f]; f[m_] := f[m] = Select[Table[10^x - y^2, {x, 0, m}, {y, 0, Ceiling[10^(x/2)]}] // Flatten // Union, 0 <= # <= max &]; f[1]; f[m = 2]; While[f[m] != f[m - 1], m++]; Print["m = ", m]; A051221 = f[m] (* _Jean-François Alcover_, May 13 2017 *)

%Y Cf. A128826.

%K nonn

%O 1,3

%A _David W. Wilson_