

A096873


Minimum diameter of an integral set of n points in the plane, no 3 on a line, no 4 on a circle.


2




OFFSET

1,4


COMMENTS

An integral set is a set where all distances between points are integers.
As of 2011, it is not known if this sequence is finite or even if a(8) exists.


REFERENCES

H. Harborth, Integral distances in point sets, Butzer, P. L. (ed.) et al., Karl der Grosse und sein Nachwirken. 1200 Jahre Kultur und Wissenschaft in Europa. Band 2: Mathematisches Wissen. Turnhout: Brepols. 213224 (1998).


LINKS

Table of n, a(n) for n=1..7.
Tobias Kreisel, Sascha Kurz, There are integral heptagons, no three points on a line, no four on a circle, preprint (2006)
T. Kreisel and S. Kurz, There are integral heptagons, no three points on a line, no four on a circle, Discrete and Computational Geometry 39 Issue 4 (2008), 786790, MR2413160
J. Solymosi and F. de Zeeuw, On a Question of Erdos and Ulam, Discrete and Computational Geometry Vol. 43 Issue 2 (2010), 393401.


CROSSREFS

Cf. A007285, A096872.
Sequence in context: A001799 A205505 A058068 * A282786 A241630 A153482
Adjacent sequences: A096870 A096871 A096872 * A096874 A096875 A096876


KEYWORD

hard,nonn,more


AUTHOR

Sascha Kurz, Jul 13 2004


EXTENSIONS

a(7) computed in [KreiselKurz].


STATUS

approved



