If n is an odd prime, a(n) = the number of primitive roots mod n, otherwise a(n) = the number of k < n divisible by at least one but not all of the prime factors of n.
A027413
If n is an odd prime, a(n) = the number of primitive roots mod n, otherwise a(n) = the number of k < n divisible by at least one but not all of the prime factors of n.
Terms
- a(0) =0a(1) =0a(2) =1a(3) =0a(4) =2a(5) =3a(6) =2a(7) =0a(8) =0a(9) =5a(10) =4a(11) =6a(12) =4a(13) =7a(14) =6a(15) =0a(16) =8a(17) =9a(18) =6a(19) =10a(20) =8a(21) =11a(22) =10a(23) =12a(24) =0a(25) =13a(26) =0a(27) =14a(28) =12a(29) =21
External references
- oeis: A027413