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%I #13 Feb 21 2015 12:37:27
%S 1,12,111,1002,12021,111222,1001001,12012012,111111111,1000000002,
%T 12000000021,111000000222,1002000002001,12021000021012,
%U 111222000222111,1001001002002002,12012012021021021,111111111222222222,1000000001000000001,12000000012000000012,111000000111000000111
%N List of ternary words obtained by expanding (1+2x)^n mod 3 and reading the coefficients starting with the constant term.
%C Arises in the study of a cellular automaton whose cells are in one of three states: 0, 1, or 2.
%H <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%e The first few polynomials are:
%e 1
%e 1+2*x
%e 1+x+x^2
%e 1+2*x^3
%e 1+2*x+2*x^3+x^4
%e 1+x+x^2+2*x^3+2*x^4+2*x^5
%e 1+x^3+x^6
%e 1+2*x+x^3+2*x^4+x^6+2*x^7
%e 1+x+x^2+x^3+x^4+x^5+x^6+x^7+x^8
%e 1+2*x^9
%e 1+2*x+2*x^9+x^10
%e 1+x+x^2+2*x^9+2*x^10+2*x^11
%e 1+2*x^3+2*x^9+x^12
%e ...
%p M:=20;
%p F:=1+2*x mod 3;
%p g:=n->expand(F^n) mod 3;
%p g2:=n->series(g(n),x,M+6);
%p for n from 0 to M do lprint(seriestolist(g2(n))); od:
%Y Cf. A255285, A255286, A182069.
%K nonn
%O 0,2
%A _N. J. A. Sloane_, Feb 13 2015
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