a(0) = 0; a(n) = a(n/3)/3 if n = a(n/3) = 0 (mod 3); a(n) = a(n-1)+1 otherwise.

Terms

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