A124158 Maximal number of edges in a rectangle visibility graph with n nodes.

0, 1, 3, 6, 10, 15, 21, 28, 34, 40, 46, 52, 58, 64, 70, 76, 82, 88, 94, 100, 106, 112, 118, 124, 130, 136, 142, 148, 154, 160, 166, 172, 178, 184, 190, 196, 202, 208, 214, 220, 226, 232, 238, 244, 250, 256, 262, 268, 274, 280, 286, 292, 298, 304, 310, 316, 322, 328, 334, 340

Offset

1,3

Comments

If Y is a 3-subset of an 2n-set X then, for n>=6, a(n+1) is the number of 3-subsets of X having at least two elements in common with Y. - Milan Janjic, Dec 16 2007

References

L. W. Beineke, Biplanar graphs: a survey, Computers Math. Applic., 34 (1997), 1-8.

Hutchinson, Joan P.; Shermer, Thomas; and Vince, Andrew; On representations of some thickness-two graphs. Comput. Geom. 13 (1999), 161-171.

Links

Table of n, a(n) for n=1..60.

Formula

If n <= 8 then n*(n-1)/2 else 6*n-20.

Crossrefs

Sequence in context: A130486 A054636 A231680 * A161208 A109444 A124157

Adjacent sequences: A124155 A124156 A124157 * A124159 A124160 A124161

Keyword

nonn

Author

N. J. A. Sloane, Dec 02 2006

Status

approved