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A083041 Number of symmetric sum-free subsets of {1,2,...,n-1} with sums taken mod n. 0
1, 2, 1, 3, 3, 4, 4, 8, 4, 14, 11, 14, 16, 31, 19, 45, 37, 56, 55, 106, 55, 164, 122, 179, 190, 353, 178, 467, 379, 648, 541 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Parker vector for K_3-free graphs.

REFERENCES

P. J. Cameron, Portrait of a typical sum-free set, Surveys in combinatorics 1987, London Math. Soc. Lecture Note Ser., 123, 1987, pp. 13-42.

LINKS

Table of n, a(n) for n=1..31.

D. A. Gewurz and F. Merola, Sequences realized as Parker vectors of oligomorphic permutation groups, J. Integer Seq., 6 (2003), 03.1.6

EXAMPLE

a(3) = 1, as {} is the only symmetric sum-free set ({1} is not symmetric, while {1,2} is not sum-free). a(4)=3; its symmetric sum-free subsets are {}, {1,3}, {2}.

CROSSREFS

Cf. A007865

Sequence in context: A027157 A112194 A238788 * A130067 A282906 A032303

Adjacent sequences:  A083038 A083039 A083040 * A083042 A083043 A083044

KEYWORD

nonn

AUTHOR

Daniele A. Gewurz (gewurz(AT)mat.uniroma1.it), Francesca Merola (merola(AT)mat.uniroma1.it), May 06 2003

STATUS

approved

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Last modified February 24 21:22 EST 2018. Contains 299628 sequences. (Running on oeis4.)