This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A327019 #6 Aug 15 2019 07:30:30
%S A327019 1,1,1,1,2,2,5,7,15,26,61
%N A327019 Number of non-isomorphic set-systems of weight n whose dual is a (strict) antichain.
%C A327019 Also the number of non-isomorphic set-systems where every vertex is the unique common element of some subset of the edges, also called non-isomorphic T_1 set-systems.
%C A327019 A set-system is a finite set of finite nonempty sets. The dual of a set-system has, for each vertex, one edge consisting of the indices (or positions) of the edges containing that vertex. For example, the dual of {{1,2},{2,3}} is {{1},{1,2},{2}}.
%C A327019 An antichain is a set of sets, none of which is a subset of any other.
%e A327019 Non-isomorphic representatives of the a(1) = 1 through a(8) = 15 multiset partitions:
%e A327019 {1} {1}{2} {1}{2}{3} {1}{2}{12} {1}{2}{3}{23} {12}{13}{23}
%e A327019 {1}{2}{3}{4} {1}{2}{3}{4}{5} {1}{2}{13}{23}
%e A327019 {1}{2}{3}{123}
%e A327019 {1}{2}{3}{4}{34}
%e A327019 {1}{2}{3}{4}{5}{6}
%e A327019 .
%e A327019 {1}{23}{24}{34} {12}{13}{24}{34}
%e A327019 {3}{12}{13}{23} {2}{13}{14}{234}
%e A327019 {1}{2}{3}{13}{23} {1}{2}{13}{24}{34}
%e A327019 {1}{2}{3}{24}{34} {1}{2}{3}{14}{234}
%e A327019 {1}{2}{3}{4}{234} {1}{2}{3}{23}{123}
%e A327019 {1}{2}{3}{4}{5}{45} {1}{2}{3}{4}{1234}
%e A327019 {1}{2}{3}{4}{5}{6}{7} {1}{2}{34}{35}{45}
%e A327019 {1}{4}{23}{24}{34}
%e A327019 {2}{3}{12}{13}{23}
%e A327019 {1}{2}{3}{4}{12}{34}
%e A327019 {1}{2}{3}{4}{24}{34}
%e A327019 {1}{2}{3}{4}{35}{45}
%e A327019 {1}{2}{3}{4}{5}{345}
%e A327019 {1}{2}{3}{4}{5}{6}{56}
%e A327019 {1}{2}{3}{4}{5}{6}{7}{8}
%Y A327019 Cf. A007716, A059523, A283877, A293993, A326961, A326965, A326974, A326976, A326977, A326979, A327012, A327018.
%K A327019 nonn,more
%O A327019 0,5
%A A327019 _Gus Wiseman_, Aug 15 2019