a(1)=1, a(n)=2*a(n-1)+1 if that number is composite, a(n)=a(n-1)+1 otherwise.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =9a(5) =10a(6) =21a(7) =22a(8) =45a(9) =91a(10) =183a(11) =184a(12) =369a(13) =370a(14) =741a(15) =742a(16) =1485a(17) =1486a(18) =2973a(19) =5947a(20) =11895a(21) =23791a(22) =47583a(23) =95167a(24) =190335a(25) =380671a(26) =761343a(27) =1522687a(28) =3045375a(29) =3045376