A136722 - OEIS

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A136722

Number of preferential arrangements (or hierarchical orderings) on the connected graphs on n unlabeled nodes.

1, 1, 2, 8, 48, 336, 3584, 54592, 1422976, 66836480, 5998884352, 1030861378560, 335994532814848, 206175878632321024, 237596569295651315712, 514414692643000188272640 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	FORMULA	`a(n)=A001349(n)*A011782(n).`
	EXAMPLE	`There are A001349(3)=2 connected graphs for n=3 unlabeled elements:` `The chain` `o-o-o` `and the triangle` `. o` `/..\` `o - o.` `There are a(3)=8 hierarchical orders on these two graphs.` `The chain gives us 6 orderings:` `o-o-o` `o` `\|` `o-o` `. o` `/..\` `o . o` `o . o` `.\./` `. o` `o-o` `\|` `o` `o` `\|` `o` `\|` `o` `The triangle gives us two orderings:` `. o` `/..\` `o - o` `o - o` `\../` `. o`
	CROSSREFS	`Cf. A001349, A011782, A136723, A034691, A075729.` `Sequence in context: A177066 A007170 A171455 * A085615 A054726 A003576` `Adjacent sequences: A136719 A136720 A136721 * A136723 A136724 A136725`
	KEYWORD	`easy,nonn`
	AUTHOR	`Thomas Wieder (thomas.wieder(AT)t-online.de), Jan 19 2008`

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Last modified February 14 13:08 EST 2012. Contains 205623 sequences.