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A175769
Maximum cardinality of isosceles sets in E^n.
0
3, 6, 8, 11, 17, 28, 30, 45
OFFSET
1,1
COMMENTS
An isosceles set is a set of points in a plane or in space, any three of which form an isosceles triangle.
In his 1946 problem Erdős notes that a(2) = 6 and asks for the value of a(3); L. M. Kelly proves that a(2) = 6 and shows that a(3) >= 9. The editors note that Kelly disproves a conjecture of Coxeter. - Charles R Greathouse IV, May 21 2021
LINKS
Paul Erdős, Problems for Solution: E735, The American Mathematical Monthly, vol. 53, no. 7 (August 1946), p. 394.
Paul Erdős and L. M. Kelly, Isosceles n-points, The American Mathematical Monthly, vol. 54, no. 4 (April 1947), pp. 227-229.
Yury J. Ionin, Isosceles Sets, The Electronic Journal of Combinatorics, Vol. 16, No. 1 (2009), R141.
CROSSREFS
Cf. A027627.
Sequence in context: A360532 A289241 A234307 * A352211 A160277 A080598
KEYWORD
nonn,more,hard
AUTHOR
John W. Layman, Sep 01 2010
EXTENSIONS
Comment corrected by John W. Layman, Sep 03 2010
STATUS
approved