%I
%S 1,2,10,20,100,101,200,201,1000,1001,1002,1010,2000,2001,2002,2010,
%T 10000,10001,10002,10010,10020,10100,10101,20000,20001,20002,20010,
%U 20020,20100,20101,100000,100001,100002,100010,100020,100100,100101,100200,100201
%N Nonzero ternary words such that any noninitial 1 is preceded by 0, and any noninitial 2 is preceded by 00.
%C This could have begun with an initial 0, but (since this is a list, and must have offset 1), we would no longer have a(1)=1, and that is needed for some related sequences.
%C The indices of words of the form 100...00 are 1, 3, 5, 9, 17, 31, ..., see the tribonacci numbers A000213.
%H N. J. A. Sloane, <a href="/A324474/b324474.txt">Table of n, a(n) for n = 1..845</a>
%e The initial terms, as a list:
%e 1
%e 2
%e 10
%e 20
%e 100
%e 101
%e 200
%e 201
%e 1000
%e 1001
%e 1002
%e 1010
%e 2000
%e 2001
%e 2002
%e 2010
%e 10000
%e ...
%Y Cf. A007089, A324475, A000213.
%K nonn,base
%O 1,2
%A _Nathan Fox_ and _N. J. A. Sloane_, Mar 09 2019
