2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 3, 2, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2 smallest prime factor of smaller of amicable pair a(n) = A020639(A002025(n)) = Lpf(A002025(n)) = sigma(A002025(n))-A002025(n). Must always be 2 or 3?