id:A055152 - OEIS Search Results

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Proper covers of an unlabeled n-set.

+0
3

0, 1, 14, 956, 9331320, 6406603065901952, 16879085743296493569230716352778240, 717956902513121252476003434439730211883694285987816199468264943161704448 (list; graph; listen)

	OFFSET	`1,3`
	LINKS	`Eric Weisstein's World of Mathematics, Proper covers`
	FORMULA	`a(n)=(A003180 (n)-2*A003180 (n-1))/4.` `Apparently a(n)=A002857(n)-A000612(n-1). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 22 2007`
	CROSSREFS	`See A007537 for labeled case. Cf. A055621.` `Sequence in context: A064345 A159871 A115458 this_sequence A064729 A123178 A160011` `Adjacent sequences: A055149 A055150 A055151 this_sequence A055153 A055154 A055155`
	KEYWORD	`easy,nonn`
	AUTHOR	`Vladeta Jovovic (vladeta(AT)eunet.rs), Jun 14 2000`
	EXTENSIONS	`More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Mar 21 2002`

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Last modified December 11 12:57 EST 2009. Contains 170656 sequences.

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