A107791 Twos order in the tribonacci substitution of three symbols.

2, 4, 7, 11, 13, 16, 18, 21, 25, 27, 30, 33, 35, 38, 42, 44, 47, 51, 53, 56, 59, 61, 64, 68, 70, 73, 75, 78, 82, 84, 87, 90, 92, 95, 99, 101, 104, 106, 109, 113, 115, 118, 121, 123, 126, 130, 132, 135, 139, 141, 144, 147, 149, 152, 156, 158, 161, 163, 166, 170, 172

Offset

0,1

Links

Table of n, a(n) for n=0..60.

Formula

1->(2), 2->{3}, 3->{1, 2, 3}, a(n) = order of appearance of twos in the substitution

Mathematica

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]] pp = p[12] a = Flatten[Table[If[pp[[j]] == 2, j, {}], {j, 1, Length[pp]}]]

Crossrefs

Cf. A000045, A000213.

Sequence in context: A206853 A229618 A087285 * A181518 A262231 A356133

Adjacent sequences: A107788 A107789 A107790 * A107792 A107793 A107794

Keyword

nonn,uned

Author

Roger L. Bagula, Jun 11 2005

Status

approved