OFFSET
1,2
COMMENTS
After first term, these are the numbers of the form (3i+2)*3^j, where i >= 0, j >= 0. - Clark Kimberling, Oct 19 2016
Old conjecture: (a(n)) = complement of A026225 after removal of the initial 1 here. [Note that following the proof of the form of its terms, A026225 has been renamed accordingly. - Peter Munn, Mar 24 2022]
The asymptotic density of this sequence is 1/2. - Amiram Eldar, Apr 03 2022
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
F. M. Dekking, Permutations of N generated by left-right filling algorithms, arXiv:2001.08915 [math.CO], 2020, see R_opos in section 2.3.
Kevin Ryde, Iterations of the Terdragon Curve, see index "TurnRight".
FORMULA
Let the sequence 1, 0, 1, 1, 0, 0, 1, 0, 1, ... (A137893) be defined as the fixed point of the morphism 1->101 and 0->100, starting from a(1)=1. The indices of 0 are 2, 5, 6, 8, 11, 14, 17, 18, ... (this sequence with first term omitted). - Philippe Deléham, Jun 27 2006
MATHEMATICA
a[b_] := Table[Mod[n/b^IntegerExponent[n, b], b], {n, 1, 160}]
p[b_, d_] := Flatten[Position[a[b], d]]
p[3, 1] (* A026225 *)
p[3, 2] (* A026179 without initial 1 *)
(* Clark Kimberling, Oct 19 2016 *)
PROG
(PARI) a(n) = { if(n>1, n=2*n-2; my(v=digits(n, 3));
for(i=1, #v, if(v[i]==1, n++;
forstep(j=#v, i, -1, if(v[j]++>2, v[j]=0, break)))));
n; } \\ Kevin Ryde, Apr 23 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved