login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

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 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

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