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OFFSET

1,2


COMMENTS

Conjecture: a(n)/n > (61sqrt(3))/26 = 2.279...
From Michel Dekking, Feb 10 2021: (Start)
This conjecture is false. In fact,
a(n)/n > (5+sqrt(17))/4 = 2.28077...
Let mu be the defining morphism for A285177, i.e,
mu(0) = 11, mu(1) = 001.
The sequence A285177 is the fixed point x = 0010010010011111... starting with 0 of mu^2:
mu^2(0) = 001001, mu^2(1) = 1111001.
The 0's in x are at positions a(1)=1, a(2)=2, a(3)=4, etc.
Now suppose that N_0(K) = n is the number of 0's in a prefix x[1,K] of length K of x. Then obviously a(n) = K +/ 6.
Also N_0(K) + N_1(K) = K, where N_1(K) is the number of 1's in x[1,K].
So
K/N_0(K) = a(n)/n +/ 6/n.
Letting n tend to infinity, we find that
a(n)/n > 1/f0,
where f0 is the frequency of 0's in x.
It is well known that these exist and are equal to the normalized eigenvector of the PerronFrobenius eigenvalue of the incidence matrix of the morphism mu.
A simple computation yields that f0 = 4/(5+sqrt(17)).
It follows that a(n)/n > (5+sqrt(17))/4.
(End)


LINKS

Clark Kimberling, Table of n, a(n) for n = 1..10000


EXAMPLE

As a word, A285177 = 001001..., in which 0 is in positions 1,2,4,5,7,...


MATHEMATICA

s = Nest[Flatten[# /. {0 > {1, 1}, 1 > {0, 0, 1}}] &, {0}, 10] (* A285117 *)
Flatten[Position[s, 0]] (* A285401 *)
Flatten[Position[s, 1]] (* A285402 *)


CROSSREFS

Cf. A285177, A285402, A285403.
Sequence in context: A277121 A325112 A102338 * A139449 A204399 A020914
Adjacent sequences: A285398 A285399 A285400 * A285402 A285403 A285404


KEYWORD

nonn,easy


AUTHOR

Clark Kimberling, Apr 26 2017


STATUS

approved



