seen = 0

head = vector(100)	\\ enough to compute a(n) up to 2^100

compute(n) = {
	my (m=1, b=binary(n));
	for (i=2, #b,
		if (b[i],
			m = lcm(m, head[i]);
		);
	);
	forstep(v=m, oo, m,
		if (!bittest(seen, v),
			if (n<=#head,
				head[n] = v;
			);
			seen += 2^v;
			return (v);
		);
	);
}

for (n=1, 10 000, print (n " " compute(n)))

quit