

A280218


Number of binary necklaces of length n with no subsequence 0000.


7



1, 2, 3, 5, 6, 11, 15, 27, 43, 75, 125, 228, 391, 707, 1262, 2285, 4119, 7525, 13691, 25111, 46033, 84740, 156123, 288529, 533670, 989305, 1835983, 3412885, 6351031, 11834623, 22074821, 41222028, 77048131, 144148859, 269913278, 505826391, 948652695, 1780473001, 3343960175, 6284560319, 11818395345
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OFFSET

1,2


COMMENTS

a(n) is the number of cyclic sequences of length n consisting of zeros and ones that do not contain four consecutive zeros provided we consider as equivalent those sequences that are cyclic shifts of each other.


LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..3521
P. Flajolet and M. Soria, The Cycle Construction, SIAM J. Discr. Math., vol. 4 (1), 1991, pp. 5860.
P. Flajolet and M. Soria, The Cycle Construction, SIAM J. Discr. Math., vol. 4 (1), 1991, pp. 5860.
Silvana Ramaj, New Results on Cyclic Compositions and Multicompositions, Master's Thesis, Georgia Southern Univ., 2021. See p. 57.
F. Ruskey, Necklaces, Lyndon words, De Bruijn sequences, etc.
F. Ruskey, Necklaces, Lyndon words, De Bruijn sequences, etc. [Cached copy, with permission, pdf format only]
F. Ruskey, Necklaces, Lyndon words, De Bruijn sequences, etc. [Cached copy, with permission, pdf format only]
L. Zhang and P. Hadjicostas, On sequences of independent Bernoulli trials avoiding the pattern '11..1', Math. Scientist, 40 (2015), 8996.


FORMULA

a(n) = (1/n) * Sum_{d divides n} totient(n/d) * A073817(d).
G.f.: Sum_{k>=1} (phi(k)/k) * log(1/(1B(x^k))) where B(x) = x*(1+x+x^2+x^3).


EXAMPLE

a(5)=6 because we have six binary cyclic sequences of length 5 that avoid four consecutive zeros: 00011, 00101, 00111, 01101, 01111, 11111.


MATHEMATICA

Table[(1/n) Sum[EulerPhi[n/d] SeriesCoefficient[(4  3 x  2 x^2  x^3)/(1  x  x^2  x^3  x^4), {x, 0, d}], {d, Divisors@ n}], {n, 41}] (* Michael De Vlieger, Dec 30 2016 *)


PROG

(PARI) N=44; x='x+O('x^N);
B(x)=x*(1+x+x^2+x^3);
Vec(sum(k=1, N, eulerphi(k)/k * log(1/(1B(x^k))))) \\ Joerg Arndt, Dec 29 2016


CROSSREFS

Cf. A000358, A073817, A093305, A280303.
Sequence in context: A039896 A180336 A034407 * A294526 A068441 A268935
Adjacent sequences: A280215 A280216 A280217 * A280219 A280220 A280221


KEYWORD

nonn


AUTHOR

Petros Hadjicostas, Dec 29 2016


STATUS

approved



