a(n) = Sum_{j|n, 1 < j < n} phi(j). Also a(n) = n - phi(n) - 1 for n > 1.

Terms

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