big = 1 000 000
s = 0
S = Set([])
unseen = 1
seen(v) = if (v < big, bit test(s, v), set search(S, v))
see(v) = if (v < big, s = bit or(s, 2^v), S = set union(S, Set([v]))); while (seen(unseen), unseen++)

base = 10

pos = vector(base, d, -oo)
nb = 0

keep(v) = {
	my (xpos=vector(base, d, -oo), xnb=0, d=digits(v, base));
	for (k=1, #d,
		xnb++;
		if (xpos[1+d[k]] >= xnb - d[k],
				return (0),
				xpos[1+d[k]] = xnb
		);
	);
	return (1);
}

accept(v) = {
	my (xpos=pos, xnb=nb, d=digits(v, base));
	for (k=1, #d,
		xnb++;
		if (xpos[1+d[k]] >= xnb - d[k],
				return (0),
				xpos[1+d[k]] = xnb
		);
	);
	pos = xpos;
	nb = xnb;
	return (1);
}

{
	for (n=1, 10 000,
		for (v=unseen, oo,
			if (!seen(v) && accept(v),
				see(v);
				print (n " " v);
				while (!keep(unseen), see(unseen));
				break;
			);
		);
	);
}

quit