a(n) = Sum_{d|n} (-1)^omega(n/d) * phi(rad(n/d)) * p(d), where p = A000041 (partition numbers).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =6a(6) =9a(7) =14a(8) =22a(9) =31a(10) =46a(11) =59a(12) =89a(13) =114a(14) =158a(15) =201a(16) =281a(17) =337a(18) =472a(19) =570a(20) =756a(21) =936a(22) =1233a(23) =1456a(24) =1926a(25) =2323a(26) =2942a(27) =3556a(28) =4537a(29) =5334