a(1)=0, a(n+1) is the smallest nonprime with sum of digits > sum of digits of a(n).

Terms

a(0) =0a(1) =1a(2) =4a(3) =6a(4) =8a(5) =9a(6) =28a(7) =38a(8) =39a(9) =49a(10) =68a(11) =69a(12) =88a(13) =98a(14) =99a(15) =289a(16) =299a(17) =399a(18) =589a(19) =689a(20) =699a(21) =799a(22) =899a(23) =999a(24) =2899a(25) =3899a(26) =3999a(27) =5899a(28) =5999a(29) =6999