%I A000401
%S A000401 0,1,2,3,4,5,6,7,8,9,10,11,12,13,15,16,17,18,19,20,21,22,23,24,25,26,
%T A000401 27,28,29,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,47,48,49,50,51,
%U A000401 52,53,54,55,57,58,59,60,61,63,64,65,66,67,68,69,70,71,72,73,74,75,76
%N A000401 Numbers of form x^2 + y^2 + 2z^2.
%C A000401 Numbers represented by quadratic form with Gram matrix [ 1, 0, 0; 0, 
               1, 0; 0, 0, 2 ].
%D A000401 L. E. Dickson, Integers represented by positive ternary quadratic forms, 
               Bull. Amer. Math. Soc., 33 (1927) 63-70. [http://projecteuclid.org/
               euclid.bams/1183491956]
%D A000401 W. Sierpinski, Elementary Theory of Numbers, (Ed. A. Schinzel) North-Holland 
               1988, see Exercise 4 on p. 395.
%H A000401 T. D. Noe, <a href="b000401.txt">Table of n, a(n) for n=1..1000</a>
%H A000401 G. Nebe and N. J. A. Sloane, <a href="http://www.research.att.com/~njas/
               lattices/tetragonalP.html">Home page for this lattice</a>
%F A000401 These are the numbers not of the form 4^k*(16*n + 14). [Dickson] - Everett 
               W. Howe, May 18 2008
%p A000401 L := [seq(0,i=1..1)]: for x from 0 to 20 do for y from 0 to 20 do for 
               z from 0 to 20 do if member(x^2+y^2+2*z^2, L)=false then L := [op(L), 
               x^2+y^2+2*z^2] fi: od: od: od: L2 := sort(L): for i from 1 to 100 
               do printf(`%d,`,L2[i]) od:
%Y A000401 Complement of A055039.
%Y A000401 Sequence in context: A065673 A077168 A102452 this_sequence A023807 A023755 
               A114886
%Y A000401 Adjacent sequences: A000398 A000399 A000400 this_sequence A000402 A000403 
               A000404
%K A000401 nonn
%O A000401 1,3
%A A000401 N. J. A. Sloane (njas(AT)research.att.com).
%E A000401 More terms from James A. Sellers (sellersj(AT)math.psu.edu), May 31 2000