A201973 Numbers of configurations of n-1 linear orderings on {1..n} up to equivalence.

1, 2, 21, 5097, 71965235

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

Table of n, a(n) for n=2..6.

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 A328993

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