D = 141

H = vector(D, n, [+oo])
V = vector(D, k, [+oo])

{
	m = 0;
	for (d = 1, D,
		for (n = 1, d,
			k = d + 1 - n;
			if (n==1 && k==1,
					v = 1,
				H[n][1] < V[k][1],
					v = H[n][1];
					H[n] = H[n][2..#H[n]],
					v = V[k][1];
					V[k] = V[k][2..#V[k]]
			);

			print (m++ " " v);
			H[n] = setunion(H[n], [2*v]);
			V[k] = setunion(V[k], [2*v+1]);
		);
	);
}

quit