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 A201973 Numbers of configurations of n-1 linear orderings on {1..n} up to equivalence. 0
 1, 2, 21, 5097, 71965235 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 COMMENTS A configuration is a set of n-1 linear orderings <_1, .., <_(n-1) on {1..n}.   A reversion of an ordering is the ordering obtained by reversing every inequality in this ordering. Two configurations are equivalent if they are equal up to: - a permutation of <_1, .., <_(n-1) - a permutation of {1..n} - some reversions of orderings REFERENCES E. Gioan, K. Sol and G. Subsol, Orientations of Simplices Determined by Orderings on the Coordinates of their Vertices, In Proc. of 23rd CCCG, 187-192, 2011. LINKS EXAMPLE For n=3, the a(3)=2 configurations up to equivalence are: (1 <_1 2 <_1 3; 1 <_2 2 <_2 3) and (1 <_1 2 <_1 3; 1 <_2 3 <_2 2). CROSSREFS Sequence in context: A276654 A114846 A195165 * A278737 A162393 A180700 Adjacent sequences:  A201970 A201971 A201972 * A201974 A201975 A201976 KEYWORD nonn AUTHOR Kevin SOl, Dec 07 2011 EXTENSIONS 71965235 added by Kevin SOl, May 30 2012 STATUS approved

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Last modified June 16 06:46 EDT 2019. Contains 324145 sequences. (Running on oeis4.)