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++)

other(p) = {
	for (v=2, oo,
		if (!seen(p^v),
			see(p^v);
			return (v);
		);
	);
}

for (n=1, 10 000, print (n " " v=if (n==1, 2, other(v))))

quit