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

W = 6
m = vector(W,k,k)
inv = vector(10 000)
u = 1

{
	v=1;
	for (n=1, oo,
		if (v<=#inv,
			inv[v]=n;
			while (inv[u],
				print (u " " inv[u]);
				if (u++>#inv,
					break (2);
				);
			);
		);
		see(v);
		w = W/gcd(v,W);
		while (seen(m[w]),
			m[w]+=w;
		);
		v=m[w];
	);
}

quit