A014456 - OEIS

A014456

Numbers represented by quadratic form with Gram matrix [ 2, 1, 0; 1, 3, 1; 0, 1, 2 ].

%I #10 Mar 31 2012 10:30:15

%S 0,2,3,4,7,8,10,11,12,15,16,18,19,20,23,24,26,27,28,31,32,34,35,36,39,

%T 40,42,43,44,47,48,50,51,52,55,58,59,60,63,64,66,67,68,71,72,74,75,76,

%U 79,80,82,83,84,87,88,90,91,92,95,96,98,99,100,103,104,106,107,108,111

%N Numbers represented by quadratic form with Gram matrix [ 2, 1, 0; 1, 3, 1; 0, 1, 2 ].

%H G. Nebe and N. J. A. Sloane, <a href="http://www.math.rwth-aachen.de/~Gabriele.Nebe/LATTICES/tetragonalI.html">Home page for this lattice</a>

%p L := [seq(0,i=1..1)]: for x from -20 to 20 do for y from -20 to 20 do for z from -20 to 20 do if member(2*x^2+2*x*y+3*y^2+2*y*z+2*z^2, L)=false then L := [op(L), 2*x^2+2*x*y +3*y^2+2*y*z+2*z^2] fi: od: od: od: L2 := sort(L): for i from 1 to 100 do printf(`%d,`,L2[i]) od:

%K nonn

%O 1,2

%A _N. J. A. Sloane_.

%E More terms from _James A. Sellers_, May 31 2000