A107641 - OEIS

%I #4 Mar 30 2012 17:34:15

%S 1,3,2,1,4,3,5,2,5,6,1,4,6,3,5,8,9,2,5,6,9,1,4,6,9,3,5,8,9,12,2,5,6,9,

%T 11,1,4,6,9,12,14,3,5,8,9,12,14,2,5,6,9,11,14,1,4,6,9,12,14,17,3,5,8,

%U 9,12,14,17,2,5,6,9,11,14,17,19,1,4,6,9,12,14,17,18

%N Order of appearance of threes in the tribonacci ( Rauzy type) substitution: triangular.

%F 1->{2}, 2->{3}, 3->{1, 2, 3}

%t s[1] = {2}; s[2] = {3};; s[3] = {1, 2, 3}; t[a_] := Flatten[s /@ a]; p[0] = {1}; p[1] = t[p[0]]; p[n_] := t[p[n - 1]] a = Table[Flatten[Table[If[(Length[p[i]]) >= j && (p[i][[j]] == 3), j, {}], {j, 1, i}]], {i, 1, 20}] MatrixForm[a] b = Flatten[a]

%Y Cf. A000073.

%K nonn,uned

%O 0,2

%A _Roger L. Bagula_, Jun 09 2005