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A028445 Number of cubefree words of length n on two letters. 11
1, 2, 4, 6, 10, 16, 24, 36, 56, 80, 118, 174, 254, 378, 554, 802, 1168, 1716, 2502, 3650, 5324, 7754, 11320, 16502, 24054, 35058, 51144, 74540, 108664, 158372, 230800, 336480, 490458, 714856, 1041910, 1518840, 2213868 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 0..47 [copied from Edlin paper]

A. E. Edlin, Cube-free words

Mari Huova, Combinatorics on Words. New Aspects on Avoidability, Defect Effect, Equations and Palindromes, Turku Centre for Computer Science, TUCS Dissertations No 172, April 2014.

K. Jarhumaki and J. Shallit, Polynomial vs Exponential Growth in Repetition-Free Binary Words, arXiv:math/0304095 [math.CO], 2003.

R. Kolpakov, Efficient Lower Bounds on the Number of Repetition-free Words, J. Integer Sequences, Vol. 10 (2007), Article 07.3.2.

A. M. Shur, Growth properties of power-free languages, Computer Science Review, Vol. 6 (2012), 187-208.

A. M. Shur, Numerical values of the growth rates of power-free languages, arXiv:1009.4415 [cs.FL], 2010.

Eric Weisstein's World of Mathematics, Cubefree Word.

FORMULA

Let L = lim a(n)^(1/n); then L exists since a(n) is submultiplicative, and 1.4575732 < L < 1.4575772869240 (Shur 2010). Empirical: L=1.4575772869237..., i.e. the upper bound is very precise. - Arseny Shur, Apr 27 2015

CROSSREFS

Cf. A007777, A082379, A082380.

Sequence in context: A098151 A132002 A211971 * A006305 A067247 A017985

Adjacent sequences:  A028442 A028443 A028444 * A028446 A028447 A028448

KEYWORD

nonn

AUTHOR

Anne Edlin (anne(AT)euclid.math.temple.edu)

EXTENSIONS

a(29)-a(36) from Lars Blomberg, Aug 22 2013

STATUS

approved

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Last modified August 29 15:02 EDT 2015. Contains 261198 sequences.