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Numbers of form x^2 + y^2 + 7z^2.
1

%I #16 Jul 08 2017 01:24:35

%S 0,1,2,4,5,7,8,9,10,11,12,13,15,16,17,18,20,23,24,25,26,27,28,29,30,

%T 32,33,34,36,37,38,39,40,41,43,44,45,46,47,48,49,50,52,53,54,56,57,58,

%U 59,60,61,62,63,64,65,67,68,69,71,72

%N Numbers of form x^2 + y^2 + 7z^2.

%t r[n_] := Reduce[n == x^2 + y^2 + 7z^2, {x, y, z}, Integers]; Reap[For[n = 0, n <= 100, n++, If[r[n] =!= False, Print[n]; Sow[n]]]][[2, 1]] (* _Jean-François Alcover_, Feb 08 2016 *)

%Y Complement of A097633.

%K nonn

%O 0,3

%A _N. J. A. Sloane_