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A121981 Number of finite maximal bifix codes of degree n on a two-letter alphabet. 0
1, 1, 3, 73, 5056783 (list; graph; refs; listen; history; internal format)
OFFSET

1,3

COMMENTS

A bifix (sometimes biprefix) code is a set of nonempty words X such that no word of X is a proper prefix or a proper suffix of another. The degree of a finite maximal bifix code X is the maximal number of parses that a word can have with respect to X.

It is known that there are finitely many finite maximal bifix codes of each degree.

REFERENCES

J. Berstel and D. Perrin, Theory of Codes, Academic Press, 1985, Chapter III.

EXAMPLE

On the alphabet {a,b}, for n=3 the a(3)=3 codes are:

{aaa,aab,aba,abb,baa,bab,bba,bbb},

{aaa,aaba,aabb,ab,baa,baba,babb,bba,bbb},

{aaa,aab,abaa,abab,abb,ba,bbaa,bbab,bbb}

CROSSREFS

Sequence in context: A119017 A002667 A145675 * A093183 A189805 A125520

Adjacent sequences:  A121978 A121979 A121980 * A121982 A121983 A121984

KEYWORD

nonn,hard

AUTHOR

Alessandro De Luca (alessandro.deluca(AT)unina.it), Feb 09 2011

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Last modified February 17 14:16 EST 2012. Contains 206034 sequences.