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 A306505 Number of non-isomorphic antichains of nonempty subsets of {1,...,n}. 11
 1, 2, 4, 9, 29, 209, 16352, 490013147 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The spanning case is A006602 or A261005. The labeled case is A014466. From Gus Wiseman, Jul 02 2019: (Start) Also the number of unlabeled maximal antichains of nonempty subsets of {1..(n + 1)}. For example, non-isomorphic representatives of the a(0) = 1 through a(3) = 9 antichains are:   {1}  {12}    {123}         {1234}        {1}{2}  {1}{23}       {1}{234}                {1}{2}{3}     {1}{2}{34}                {12}{13}{23}  {1}{2}{3}{4}                              {12}{134}{234}                              {1}{23}{24}{34}                              {12}{13}{14}{234}                              {123}{124}{134}{234}                              {12}{13}{14}{23}{24}{34} (End) LINKS FORMULA a(n) = A003182(n) - 1. Partial sums of A006602 minus 1. EXAMPLE Non-isomorphic representatives of the a(0) = 1 through a(3) = 9 antichains:   {}  {}     {}         {}       {{1}}  {{1}}      {{1}}              {{1,2}}    {{1,2}}              {{1},{2}}  {{1},{2}}                         {{1,2,3}}                         {{1},{2,3}}                         {{1},{2},{3}}                         {{1,3},{2,3}}                         {{1,2},{1,3},{2,3}} CROSSREFS Cf. A000372, A003182, A006126, A006602, A014466, A261005, A293606, A293993, A304996, A305000, A305001, A305857, A317674, A319721, A320449, A321679. Cf. A007363, A306007, A307249, A326358, A326359, A326360, A326363. Sequence in context: A300491 A229686 A208965 * A243789 A214935 A092329 Adjacent sequences:  A306502 A306503 A306504 * A306506 A306507 A306508 KEYWORD nonn,more AUTHOR Gus Wiseman, Feb 20 2019 STATUS approved

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Last modified January 18 19:46 EST 2020. Contains 331030 sequences. (Running on oeis4.)