s = 0
unseen = 1
seen(v) = bit test(s, v)
see(v) = s = bit or(s, 2^v); while (seen(unseen), unseen++)

T = matrix(W=100*2+1,W)
z0 = (1+I)*(W\2+1)

get(z)   = my (x=real(z+z0),y=imag(z+z0)); if (min(x,y)>0 && max(x,y)<=#T, T[x,y], 0)
set(z,v) = my (x=real(z+z0),y=imag(z+z0)); see(T[x,y]=v)

dz = vector(4, k, I^k)

compute(z) = {
	my (neighbors=1);

	for (i=1, #dz,
		my (zz=z+dz[i], vv=get(zz));
		if (vv,
			neighbors *= vv;
		);
	);

	my (allow2 = !seen(2) || neighbors%2==0);
	my (allow3 = !seen(3) || neighbors%3==0);

	for (v=unseen, oo,
		if (!seen(v) && (allow2 || v%2) && (allow3 || v%3),
			return (v);
		);
	);
}

{
	z=0;
	n=0;
	dir=1;
	for (w=1, oo,
		for (t=1, 2,
			for (i=1, w,
				print (n++ " " v = compute(z));

				if (n==#T^2,
					break (3);
				);
				set(z,v);

				z+=dir;
			);
			dir*=I;
		);
	);
}

quit