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A058211 Numbers n such that there is an arrangement of n points in the plane such that no point is on >= n/2 connecting lines. +0
1
9, 15, 19, 25, 31, 37 (list; graph; listen)
OFFSET

1,1

COMMENT

Counterexamples to a conjecture of Dirac.

REFERENCES

H. T. Croft, K. J. Falconer and R. K. Guy, Unsolved Problems in Geometry, F12.

CROSSREFS

Sequence in context: A118236 A070876 A161163 this_sequence A038599 A079364 A160666

Adjacent sequences: A058208 A058209 A058210 this_sequence A058212 A058213 A058214

KEYWORD

nonn,nice,hard

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), Nov 30 2000

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Last modified December 18 21:37 EST 2009. Contains 171024 sequences.


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