[seqfan] Re: computation for D4 lattice (A117216)

[Joerg Arndt]

* Richard Mathar <mathar at strw.leidenuniv.nl> [Feb 04. 2010 10:24]:
> [...]

Number of points in the standard root system
 version of the D_4 lattice having L_infinity norm n.
http://oeis.org/classic/A117216

m=6

va=vector(m);    \\ == [abs(w), abs(x), abs(y), abs(z) ]
vc=vector(m+1);  \\ count

{
for (w=-m,m,
    va[1] = abs(w);

    for (x=-m,m,
        va[2] = abs(x);
        sx = w + x;

        for (y=-m,m,
            va[3] = abs(y);
            sy = sx + y;

            for (z=-m,m,
                sz = sy + z;
                if ( bitand(sz,1), next() );  \\ only even sum

                va[4] = abs(z);
                d = vecmax(va);  \\ infinity (max) norm
                vc[1+d] += 1;  \\ count
                );
        );
    );
);
}

vc  \\ gives
\\ [1, 40, 272, 888, 2080, 4040, 6960]
\\  0,  1,  2,   3,    4,    5,    6

... in disagreement for n==2
Someone please check.