N-Cluster
A Lattice Point configuration with no three points Collinear and no four Concyclic. An example is the6-cluster (0, 0), (132, 
), (546, 
), (960, ), (1155, 540), (546, 1120). Call the Radius of thesmallest Circle centered at one of the points of an N-cluster which contains all the points in the N-cluster theExtent. Noll and Bell (1989) found 91 nonequivalent prime 6-clusters of Extent less than 
, but found no7-clusters.
References
Guy, R. K. Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, p. 187, 1994. Noll, L. C. and Bell, D. I. ``
-clusters for 
.'' Math. Comput. 53, 439-444, 1989.