a(1)=1, a(n)= 1 + Sum a(p), p prime, p | n-1.

Terms

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