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

other(pp,p) = {
	for (v=unseen, oo,
		if (!seen(v),
			if (gcd(pp,p)>1 || gcd(pp,v)>1 || gcd(p,v)>1,
				return (v);
			);
		);
	);
}

{
	for (n=1, 10 000,
		see(v = if (n<=2, unseen, other(pp,p)));
		print (n " " v);
		[pp,p]=[p,v];
	);
}

quit