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A124158
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Maximal number of edges in a rectangle visibility graph with n nodes.
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2
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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
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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COMMENTS
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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
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REFERENCES
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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.
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LINKS
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Table of n, a(n) for n=1..60.
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FORMULA
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If n <= 8 then n*(n-1)/2 else 6*n-20.
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CROSSREFS
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Sequence in context: A130486 A054636 A231680 * A161208 A109444 A124157
Adjacent sequences: A124155 A124156 A124157 * A124159 A124160 A124161
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane, Dec 02 2006
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STATUS
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approved
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