First order recursion: a(0) = 1; a(n) = phi(n) - a(n-1) = A000010(n) - a(n-1).

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =1a(5) =3a(6) =-1a(7) =7a(8) =-3a(9) =9a(10) =-5a(11) =15a(12) =-11a(13) =23a(14) =-17a(15) =25a(16) =-17a(17) =33a(18) =-27a(19) =45a(20) =-37a(21) =49a(22) =-39a(23) =61a(24) =-53a(25) =73a(26) =-61a(27) =79a(28) =-67a(29) =95