a(n) is the least k such that the base-3 representation of n begins at s(k), where s=A030363.

Terms

a(0) =1a(1) =2a(2) =3a(3) =9a(4) =1a(5) =19a(6) =2a(7) =6a(8) =23a(9) =3a(10) =15a(11) =22a(12) =9a(13) =10a(14) =18a(15) =1a(16) =5a(17) =19a(18) =57a(19) =55a(20) =2a(21) =8a(22) =17a(23) =68a(24) =7a(25) =6a(26) =80a(27) =51a(28) =23a(29) =13