OFFSET

0,5

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}}.

EXAMPLE

Non-isomorphic representatives of the a(1) = 1 through a(4) = 5 antichain covers:

1: {{1}}

3: {{1,2},{1,3},{2,3}}

4: {{1,2},{1,3},{2,4},{3,4}}

{{1,2},{1,3},{1,4},{2,3,4}}

{{1,3},{1,4},{2,3},{2,4},{3,4}}

{{1,2,3},{1,2,4},{1,3,4},{2,3,4}}

{{1,2},{1,3},{1,4},{2,3},{2,4},{3,4}}

CROSSREFS

KEYWORD

nonn,more

AUTHOR

Gus Wiseman, Sep 25 2018

STATUS

approved