a(n) = Sum_{d|n} phi(d)*mu(n/d).

Terms

a(0) =0a(1) =1a(2) =0a(3) =1a(4) =1a(5) =3a(6) =0a(7) =5a(8) =2a(9) =4a(10) =0a(11) =9a(12) =1a(13) =11a(14) =0a(15) =3a(16) =4a(17) =15a(18) =0a(19) =17a(20) =3a(21) =5a(22) =0a(23) =21a(24) =2a(25) =16a(26) =0a(27) =12a(28) =5a(29) =27