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A238109 List of prefix-normal words over 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.

REFERENCES

Peter Burcsi, G Fici, Z Lipták, F Ruskey, J Sawada, On prefix normal words and prefix normal forms, Preprint, 2016; http://www.cis.uoguelph.ca/~sawada/papers/pnf.pdf

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, arXiv:1401.6346 [cs.DS], 2014.

G. Fici and Zs. Lipták, On Prefix Normal Words, Research Report ISRN I3S/RR-2010-03-FR, March 2011.

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

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 November 19 07:16 EST 2017. Contains 294916 sequences.