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. 213-224 (1998).
LINKS
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), 786-790, MR2413160
J. Solymosi and F. de Zeeuw, On a Question of Erdos and Ulam, Discrete and Computational Geometry Vol. 43 Issue 2 (2010), 393-401.
CROSSREFS
KEYWORD
hard,nonn,more
AUTHOR
Sascha Kurz, Jul 13 2004
EXTENSIONS
a(7) computed in [Kreisel-Kurz].
STATUS
approved