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 A319623 Number of connected antichain covers of n vertices by distinct sets whose dual is also an antichain of distinct sets. 0
 1, 1, 0, 1, 15, 1957 (list; graph; refs; listen; history; text; internal format)
 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}}. LINKS EXAMPLE Non-isomorphic representatives of the a(1) = 1 through a(4) = 15 antichain covers: 1: {{1}} 3: {{1,2},{1,3},{2,3}} 4: {{1,2},{1,3},{2,4},{3,4}}    {{1,3},{1,4},{2,3},{2,4}}    {{1,2},{1,4},{2,3},{3,4}}    {{1,4},{2,4},{3,4},{1,2,3}}    {{1,3},{2,3},{3,4},{1,2,4}}    {{1,2},{2,3},{2,4},{1,3,4}}    {{1,2},{1,3},{1,4},{2,3,4}}    {{1,3},{1,4},{2,3},{2,4},{3,4}}    {{1,2},{1,4},{2,3},{2,4},{3,4}}    {{1,2},{1,3},{2,3},{2,4},{3,4}}    {{1,2},{1,3},{1,4},{2,4},{3,4}}    {{1,2},{1,3},{1,4},{2,3},{3,4}}    {{1,2},{1,3},{1,4},{2,3},{2,4}}    {{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, A056156, A059201, A283877, A316980, A316983, A318099, A319557, A319558, A319565, A319616-A319646, A300913. Sequence in context: A110103 A232305 A282946 * A208875 A199098 A208784 Adjacent sequences:  A319620 A319621 A319622 * A319624 A319625 A319626 KEYWORD nonn,more AUTHOR Gus Wiseman, Sep 25 2018 STATUS approved

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Last modified April 12 18:52 EDT 2021. Contains 342931 sequences. (Running on oeis4.)