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A319633 Number of antichain covers of n vertices by distinct sets whose dual is also an antichain of (not necessarily distinct) sets. 0
1, 1, 2, 6, 40, 2309 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

The dual of a multiset partition has, for each vertex, one block consisting of the indices (or positions) of the blocks containing that vertex, counted with multiplicity. For example, the dual of {{1,2},{2,2}} is {{1},{1,2,2}}.

LINKS

Table of n, a(n) for n=0..5.

EXAMPLE

The a(3) = 6 antichain covers:

   {{1,2,3}}

   {{3},{1,2}}

   {{2},{1,3}}

   {{1},{2,3}}

   {{1},{2},{3}}

   {{1,2},{1,3},{2,3}}

CROSSREFS

Cf. A006126, A007716, A049311, A059201, A283877, A293606, A316980, A316983, A318099, A319558, A319616-A319646, A300913.

Sequence in context: A051185 A118623 A000612 * A326268 A096138 A004153

Adjacent sequences:  A319630 A319631 A319632 * A319634 A319635 A319636

KEYWORD

nonn,more

AUTHOR

Gus Wiseman, Sep 25 2018

STATUS

approved

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Last modified May 27 06:28 EDT 2020. Contains 334649 sequences. (Running on oeis4.)