id:A053458 - OEIS Search Results

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Open disk numbers (version 3): a(n)= number of points (i+j/2,j*sqrt(3)/2), i,j integers (triangular grid) contained in a open disk of diameter n, centered at (0,0).

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0, 1, 1, 7, 13, 19, 31, 43, 55, 73, 85, 109, 121, 151, 169, 199, 235, 253, 295, 313, 361, 397, 433, 475, 511, 571, 595, 661, 703, 757, 817, 859, 925, 979, 1039, 1111, 1159, 1237, 1285, 1381, 1453, 1519, 1597, 1663, 1759, 1813, 1915, 1993, 2077, 2173, 2257 (list; graph; listen)

	OFFSET	`0,4`
	COMMENT	`a(n)/(n/2)^2 --> Pi*2/sqrt(3)`
	CROSSREFS	`A053416, A053456-A053459.` `Sequence in context: A040038 A081765 A091180 this_sequence A040058 A023255 A122482` `Adjacent sequences: A053455 A053456 A053457 this_sequence A053459 A053460 A053461`
	KEYWORD	`easy,nonn`
	AUTHOR	`Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Jan 13 2000`

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Last modified September 6 16:04 EDT 2008. Contains 143483 sequences.

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