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Search: id:A144873
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| A144873 |
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If n mod 8 = 0 or n mod 10 = 0 then floor(n^2/4)+n otherwise floor(n^2/4)+n-1. |
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+0
1
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| 0, 0, 2, 4, 7, 10, 14, 18, 24, 28, 35, 40, 47, 54, 62, 70, 80, 88, 98, 108, 120, 130, 142, 154, 168, 180, 194, 208, 223, 238, 255, 270, 288, 304, 322, 340, 359, 378, 398, 418, 440, 460, 482, 504, 527, 550, 574, 598, 624, 648, 675, 700, 727, 754, 782, 810, 840, 868, 898, 928
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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For n >= 5, this is the maximal number of pairs of points at unit distance in a set of n points in R^4.
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REFERENCES
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K. J. Swanepoel, Unit distances and diameters in Euclidean spaces, Discrete Comput. Geom., 41 (No. 1, 2009), 1-27.
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FORMULA
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a(n)=2*a(n-1)-a(n-2)+a(n-40)-2*a(n-41)+a(n-42). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 13 2009]
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MAPLE
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f:=proc(n) if n mod 8 = 0 or n mod 10 = 0 then floor(n^2/4)+n else floor(n^2/4)+n-1; fi; end;
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CROSSREFS
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Sequence in context: A130251 A088236 A014616 this_sequence A120679 A145106 A127723
Adjacent sequences: A144870 A144871 A144872 this_sequence A144874 A144875 A144876
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Feb 13 2009
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