id:A072446 - OEIS Search Results

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Number of subsets S of the power set P{1,2,...,n} such that: {1}, {2},..., {n} are all elements of S; if X and Y are elements of S and X and Y have a non-empty intersection, then the union of X and Y is an element of S.

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1, 2, 12, 420, 254076, 17199454920 (list; graph; listen)

	OFFSET	`1,2`
	LINKS	`Wim van Dam, Sub Power Set Sequences`
	EXAMPLE	`a(3)=12 because of the 12 sets: {{1}, {2}, {3}}; {{1}, {2}, {3}, {1, 2}}; {{1}, {2}, {3}, {1, 3}}; {{1}, {2}, {3}, {2, 3}}; {{1}, {2}, {3}, {1, 2, 3}}; {{1}, {2}, {3}, {1, 2}, {1, 2, 3}}; {{1}, {2}, {3}, {1, 3}, {1, 2, 3}}; {{1}, {2}, {3}, {2, 3}, {1, 2, 3}}; {{1}, {2}, {3}, {1, 2}, {1, 3}, {1, 2, 3}}; {{1}, {2}, {3}, {1, 2}, {2, 3}, {1, 2, 3}}; {{1}, {2}, {3}, {1, 3}, {2, 3}, {1, 2, 3}}; {{1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3}}.`
	CROSSREFS	`Cf. A072444, A072445, A072447.` `Adjacent sequences: A072443 A072444 A072445 this_sequence A072447 A072448 A072449` `Sequence in context: A156509 A051009 A060942 this_sequence A015181 A012378 A012383`
	KEYWORD	`nonn`
	AUTHOR	`Wim van Dam (vandam(AT)cs.berkeley.edu), Jun 18 2002`

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Last modified July 4 09:27 EDT 2009. Contains 160562 sequences.

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