a(n) = (n-th number that is 1 or prime) - (n-th composite number).

Terms

a(0) =-3a(1) =-4a(2) =-5a(3) =-4a(4) =-3a(5) =-1a(6) =-1a(7) =2a(8) =3a(9) =5a(10) =9a(11) =10a(12) =15a(13) =17a(14) =18a(15) =21a(16) =26a(17) =31a(18) =31a(19) =35a(20) =38a(21) =39a(22) =44a(23) =47a(24) =51a(25) =58a(26) =61a(27) =61a(28) =63a(29) =64