big limit = 100 000
big values = Set([])
small values = vector(4, i, [])

see index(z) = {
	my (s=1, x=real(z), y=imag(z));
	if (x<1,
		s += 1;
		x = 1-x;
	);
	if (y<0,
		s += 2;
		y = -y;
	);
	return ([s,x,y]);
}

see(z) = {
	my (index = see index(z));
	if (max(index[2],index[3]) > big limit,
		big values = set union(big values, Set([z])),
		if (#small values[index[1]] < index[2],
			small values[index[1]] = concat(small values[index[1]], vector(index[2] - #small values[index[1]]))
		);
		small values[index[1]][index[2]] = bit or(small values[index[1]][index[2]], 2^index[3])
	);
}

seen(z) = {
	my (index = see index(z));
	if (max(index[2],index[3]) > big limit,
		return (set search(big values, z)),
		if (#small values[index[1]] < index[2],
			return (0),
			return (bit test(small values[index[1]][index[2]], index[3]))
		);
	);
}

dz = [2+I, 2-I]
dz = concat(vector(4, k, dz*I^k))
neighbours(z) = vector(#dz, k, z+dz[k]);
newcomers(z) = select(zz -> !seen(zz) && #select(seen, neighbours(zz))==1, neighbours(z))

allocate mem(2^30)

gen = Set(0)
nb = 0

{
	mx = 2^13;
	for (n=0, mx,
		print (n " " nb);

		nb += #gen;

		for (i=1, #gen,
			see(gen[i]);
		);

		if (n!=mx,
			gen = Set(concat(apply(newcomers, gen)))
		);
	);
}

quit