a(0) = 1; a(n) = Sum_{0 <= k < n and gcd(k, n) != 1} a(k).

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =2a(5) =1a(6) =5a(7) =1a(8) =9a(9) =7a(10) =19a(11) =1a(12) =45a(13) =1a(14) =83a(15) =79a(16) =165a(17) =1a(18) =417a(19) =1a(20) =827a(21) =639a(22) =1575a(23) =1a(24) =3875a(25) =927a(26) =7025a(27) =5069a(28) =14689a(29) =1