a(n) = Sum_{d|2n+1} phi(d)*mu(d).

Terms

a(0) =1a(1) =-1a(2) =-3a(3) =-5a(4) =-1a(5) =-9a(6) =-11a(7) =3a(8) =-15a(9) =-17a(10) =5a(11) =-21a(12) =-3a(13) =-1a(14) =-27a(15) =-29a(16) =9a(17) =15a(18) =-35a(19) =11a(20) =-39a(21) =-41a(22) =3a(23) =-45a(24) =-5a(25) =15a(26) =-51a(27) =27a(28) =17a(29) =-57