a(n) = (prime(n+2)-1)/6 if this is an integer or (prime(n+2)+ 1)/6 otherwise.

Terms

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