# Added # https://oeis.org/A058026 # 1, 0, 1, 0, 3, 0, 5, 0, 3, 0, 9, 0, 11, 0, 3, 0, 15, 0, 17, 0, 5, 0 a(n) = phi(n) * Sum_{d|n} mu(d) / phi(d), where mu(k) is the Moebius function and phi(k) is the Euler totient function. - ~~~~ # Sidef program func foo(n) { euler_phi(n) * n.divisors.sum { |d| mobius(d) / euler_phi(d) } } say 30.of { foo(_) }
