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 A327425 #4 Sep 11 2019 20:22:28
%S A327425 1,1,1,2,6,54
%N A327425 Number of unlabeled antichains of nonempty sets covering n vertices where every two vertices appear together in some edge (cointersecting).
%C A327425 An antichain is a set of sets, none of which is a subset of any other. It is covering if there are no isolated vertices.
%e A327425 Non-isomorphic representatives of the a(1) = 1 through a(4) = 6 antichains:
%e A327425 {1} {12} {123} {1234}
%e A327425 {12}{13}{23} {12}{134}{234}
%e A327425 {124}{134}{234}
%e A327425 {12}{13}{14}{234}
%e A327425 {123}{124}{134}{234}
%e A327425 {12}{13}{14}{23}{24}{34}
%Y A327425 The labeled version is A327020.
%Y A327425 Unlabeled covering antichains are A261005.
%Y A327425 The weighted version is A327060.
%Y A327425 Cf. A006126, A014466, A055621, A293606, A293993, A305844, A307249, A319639, A326704, A327057, A327058, A327358, A327359.
%K A327425 nonn,more
%O A327425 0,4
%A A327425 _Gus Wiseman_, Sep 11 2019