lim = 25 000
seen = 0
unseen = 1
see(v) = if (v < lim && !bittest(seen, v), seen += 2^v; while (bittest(seen, unseen), unseen++); if (unseen==lim, quit))

combine(x,y) = x * 10^#digits(y) + y

{
	a = vector(10 000);
	for (n=1, #a,
		print (n " " a[n] = unseen);
		see(a[n]);
		for (k=1, n-1,
			see(combine(a[k], a[n]));
			see(combine(a[n], a[k]));
		);
	);
}

quit