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 A305857 Number of unlabeled intersecting antichains on up to n vertices. 16
 1, 2, 3, 6, 15, 87, 3528, 47174113 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS An intersecting antichain S is a finite set of finite nonempty sets (edges), any two of which have a nonempty intersection, and none of which is a subset of any other. LINKS FORMULA a(n) = A305855(0) + A305855(1) + ... + A305855(n). - Brendan McKay, May 11 2020 EXAMPLE Non-isomorphic representatives of the a(4) = 15 intersecting antichains:   {}   {{1}}   {{1,2}}   {{1,2,3}}   {{1,2,3,4}}   {{1,3},{2,3}}   {{1,4},{2,3,4}}   {{1,3,4},{2,3,4}}   {{1,2},{1,3},{2,3}}   {{1,4},{2,4},{3,4}}   {{1,3},{1,4},{2,3,4}}   {{1,2},{1,3,4},{2,3,4}}   {{1,2,4},{1,3,4},{2,3,4}}   {{1,2},{1,3},{1,4},{2,3,4}}   {{1,2,3},{1,2,4},{1,3,4},{2,3,4}} CROSSREFS Cf. A001206, A006126, A051185, A261006, A283877, A304998, A305843, A305844, A305854, A305855, A305856. Sequence in context: A116632 A214343 A007364 * A014627 A145781 A109162 Adjacent sequences:  A305854 A305855 A305856 * A305858 A305859 A305860 KEYWORD nonn,more AUTHOR Gus Wiseman, Jun 11 2018 EXTENSIONS a(6) from Andrew Howroyd, Aug 13 2019 a(7) from Brendan McKay, May 11 2020 STATUS approved

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Last modified December 1 16:44 EST 2021. Contains 349430 sequences. (Running on oeis4.)