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 A136722 Number of preferential arrangements (or hierarchical orderings) on the connected graphs on n unlabeled nodes. 2
 1, 1, 2, 8, 48, 336, 3584, 54592, 1422976, 66836480, 5998884352, 1030861378560, 335994532814848, 206175878632321024, 237596569295651315712, 514414692643000188272640, 2096154545790162572944244736, 16113456361117058761983824232448, 234269143891823701379016369973493760 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS 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: A228568 A007170 A171455 * A085615 A054726 A003576 Adjacent sequences:  A136719 A136720 A136721 * A136723 A136724 A136725 KEYWORD easy,nonn AUTHOR Thomas Wieder, Jan 19 2008 EXTENSIONS More terms from Alois P. Heinz, Apr 21 2012 STATUS approved

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Last modified January 18 07:12 EST 2019. Contains 319269 sequences. (Running on oeis4.)