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A238109 List of prefix-normal words over the alphabet {1,2}. 3
1, 2, 11, 12, 22, 111, 112, 121, 122, 222, 1111, 1112, 1121, 1122, 1212, 1221, 1222, 2222, 11111, 11112, 11121, 11122, 11211, 11212, 11221, 11222, 12121, 12122, 12212, 12221, 12222, 22222, 111111, 111112, 111121, 111122, 111211, 111212, 111221, 111222, 112112 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A word of length n over the alphabet {a,b} is prefix-normal if for all 1 <= k <= n, no factor of length k has more a's than the prefix of length k. For example, abbabab is not prefix-normal because aba has more a's than abb.

LINKS

Rémy Sigrist, Table of n, a(n) for n = 1..16906 (terms up to length 16)

P. Burcsi, G. Fici, Zs. Lipták, F. Ruskey and J. Sawada, On Combinatorial Generation of Prefix Normal Words, Combinatorial Pattern Matching 2014, Lecture Notes in Computer Science 8486, 60-69, 2014.

P. Burcsi, G. Fici, Zs. Lipták, F. Ruskey, J. Sawada, On prefix normal words and prefix normal forms, Theoretical Computer Science, Volume 659, 10 January 2017, Pages 1-13.

G. Fici and Zs. Lipták, On Prefix Normal Words, Developments in Language Theory 2011, Lecture Notes in Computer Science 6795, 228-238, 2011.

CROSSREFS

Cf. A194850.

Sequence in context: A213975 A137001 A136996 * A113720 A034118 A140148

Adjacent sequences:  A238106 A238107 A238108 * A238110 A238111 A238112

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Mar 02 2014

EXTENSIONS

More terms from Rémy Sigrist, Feb 12 2017

STATUS

approved

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Last modified July 18 23:45 EDT 2018. Contains 312766 sequences. (Running on oeis4.)