Smallest number not the concatenation of consecutive earlier terms.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =6a(6) =7a(7) =8a(8) =9a(9) =10a(10) =11a(11) =13a(12) =14a(13) =15a(14) =16a(15) =17a(16) =18a(17) =19a(18) =20a(19) =21a(20) =22a(21) =24a(22) =25a(23) =26a(24) =27a(25) =28a(26) =29a(27) =30a(28) =31a(29) =32