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 A319621 Number of non-isomorphic connected antichain covers of n vertices by distinct sets whose dual is also an antichain of (not necessarily distinct) sets. 0
 1, 1, 1, 2, 7, 73 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 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 EXAMPLE Non-isomorphic representatives of the a(1) = 1 through a(4) = 7 antichain covers:   {{1}}  {{1,2}}  {{1,2,3}}            {{1,2,3,4}}                   {{1,2},{1,3},{2,3}}  {{1,2},{1,3,4},{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 Cf. A006126, A007716, A007718, A049311, A056156, A059201, A316980, A316983, A318099, A319557, A319565, A319616-A319646, A300913. Sequence in context: A141315 A215637 A119811 * A167526 A064646 A144905 Adjacent sequences:  A319618 A319619 A319620 * A319622 A319623 A319624 KEYWORD nonn,more AUTHOR Gus Wiseman, Sep 25 2018 STATUS approved

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Last modified April 22 19:11 EDT 2021. Contains 343177 sequences. (Running on oeis4.)