A107640 - OEIS

%I #6 Mar 20 2024 05:07:11

%S 1,2,1,4,3,5,2,4,1,4,3,5,8,2,4,7,1,4,8,10,3,5,8,11,2,4,7,11,1,4,8,10,

%T 13,3,5,8,11,13,2,4,7,11,13,1,4,8,10,13,16,3,5,8,11,13,16,2,4,7,11,13,

%U 16,18,1,4,8,10,13,16,18,3,5,8,11,13,16,20

%N Order of appearance of twos 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] =

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

%Y Cf. A000073.

%K nonn,uned,tabf

%O 0,2

%A _Roger L. Bagula_, Jun 09 2005