a = vector(100 000)
rem = vector(#a)
inv = []

other(n) = {
	for (v=1, oo,
		if (#inv<v,
			inv = concat(inv, [[]]);
		);

		my (ok=1);
		for (k=1, #inv[v],
			my (m=2*inv[v][k]-n);
			if (m>0 && rem[m]==0,
					ok=0;
					break,
				m<=0,
					inv[v] = inv[v][1..k-1];
					break
			);
		);

		if (ok,
			for (k=1, #inv[v],
				my (m=2*inv[v][k]-n);
				rem[m]--
			);
			inv[v] = concat(n, inv[v]);
			return (v);
		);
	);
}

{
	my (k = 0);
	for (n=1, #a,
		rem[n] = a[n] = other(n);
		if (a[n]==1,
			print (k++ " " n);
		);
	);
}

quit