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 A097633 Numbers not of form x^2 + y^2 + 7z^2. 2

%I

%S 3,6,14,19,21,22,31,35,42,51,55,66,70,84,91,94,119,133,139,140,142,

%T 147,154,159,166,168,182,189,214,217,231,235,238,266,280,283,287,294,

%U 315,322,329,336,364,378,385,406,413,427,434,439,462,476,483,511,525

%N Numbers not 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 <= 600, n++, If[r[n] == False, Print[n]; Sow[n]]]][[2, 1]] (* _Jean-François Alcover_, Feb 08 2016 *)

%t Take[Module[{c=With[{nn=30},Union[Flatten[Table[x^2+y^2+7z^2,{x,0,nn},{y,0,nn},{z,0,nn}]]]]},Complement[Range[Max[c]],c]],60] (* _Harvey P. Dale_, Dec 16 2018 *)

%Y Complement of A000394.

%K nonn

%O 1,1

%A _Ralf Stephan_, Aug 20 2004

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Last modified August 2 18:31 EDT 2021. Contains 346428 sequences. (Running on oeis4.)