id:A081000 - OEIS Search Results

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n is a member if and only if it ranks among top n positive integers in centrality (cf. A080997 for fuller description of this concept).

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5

1, 2, 3, 4, 6, 8, 10, 12, 14, 15, 16, 18, 20, 21, 24, 27, 28, 30, 32, 36, 40, 42, 44, 45, 48, 50, 52, 54, 56, 60, 63, 64, 66, 68, 70, 72, 75, 76, 78, 80, 84, 88, 90, 96, 98, 99, 100, 102, 104, 105, 108, 110, 112, 114, 117, 120 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`1, 2, 3, 4, 21 and 27 are currently the only known examples of n that rank exactly n-th in centrality; it is not known whether there are others.`
	FORMULA	`The formula for the centrality of an integer is A018804(n)/n^2; see also A080997.`
	CROSSREFS	`Cf. A080997, A080998, also A081029, the highly central integers (a subset of this sequence). Complement is A081001.` `Adjacent sequences: A080997 A080998 A080999 this_sequence A081001 A081002 A081003` `Sequence in context: A047418 A026508 A026281 this_sequence A064377 A034884 A137291`
	KEYWORD	`nonn`
	AUTHOR	`Matthew Vandermast (ghodges14(AT)comcast.net), Mar 02 2003`

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Last modified October 11 09:12 EDT 2008. Contains 144832 sequences.

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