

A046873


Number of total orders extending inclusion on P({1,...,n}).


2




OFFSET

0,3


COMMENTS

Trivial upper bound: a(n) <= (2^n)!.
Number of linear extensions of the boolean lattice 2^n.  Mitch Harris, Dec 27 2005
The number of vertices in the representation of all linear extensions in a distributive lattice are the Dedekind numbers (A000372) and the number of edges constitutes A118077.  Oliver Wienand, Apr 11 2006
A lower bound is A051459(n) = Product_{k=0..n} binomial(n,k)! <= a(n).  Geoffrey Critzer, May 20 2018


LINKS

J. Daniel Christensen, Table of n, a(n) for n = 0..7
Graham R. Brightwell, and Prasad Tetali, The number of linear extensions of the Boolean lattice, Order, v. 20 (2003), no. 4, 333345. (Gives asymptotics.)
Andries E. Brouwer and J. Daniel Christensen, Counterexamples to conjectures about Subset Takeaway and counting linear extensions of a Boolean lattice, arXiv:1702.03018 [math.CO], 2017. (Gives n=7 result.)
Sha, Ji Chang and Kleitman, D. J., The number of linear extensions of subset ordering, Discrete Math. 63 (1987), no. 23, 271278.


EXAMPLE

a(2)=2 because either {}<{0}<{1}<{0,1} or {}<{1}<{0}<{0,1}.


CROSSREFS

Cf. A001206, A114717, A000372, A118077.
Sequence in context: A057527 A166475 A152688 * A261125 A164334 A100540
Adjacent sequences: A046870 A046871 A046872 * A046874 A046875 A046876


KEYWORD

nonn,nice


AUTHOR

David A. Madore


EXTENSIONS

a(5) from Oliver Wienand, Apr 11 2006, using Python and an inference method for computing the set of linear extensions of arbitrary posets. Using the same method on a compute server generated a(6) on Dec 05 2010.
a(7) from J. Daniel Christensen, Feb 13 2017, based on BrouwerChristensen work cited above, using C.


STATUS

approved



