For n >= 2, n = Sum_{n/2<=k<=n, gcd(k,n)=1} a(k).

Terms

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