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 A305857 #19 May 11 2020 09:50:17
%S A305857 1,2,3,6,15,87,3528,47174113
%N A305857 Number of unlabeled intersecting antichains on up to n vertices.
%C A305857 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.
%F A305857 a(n) = A305855(0) + A305855(1) + ... + A305855(n). - _Brendan McKay_, May 11 2020
%e A305857 Non-isomorphic representatives of the a(4) = 15 intersecting antichains:
%e A305857 {}
%e A305857 {{1}}
%e A305857 {{1,2}}
%e A305857 {{1,2,3}}
%e A305857 {{1,2,3,4}}
%e A305857 {{1,3},{2,3}}
%e A305857 {{1,4},{2,3,4}}
%e A305857 {{1,3,4},{2,3,4}}
%e A305857 {{1,2},{1,3},{2,3}}
%e A305857 {{1,4},{2,4},{3,4}}
%e A305857 {{1,3},{1,4},{2,3,4}}
%e A305857 {{1,2},{1,3,4},{2,3,4}}
%e A305857 {{1,2,4},{1,3,4},{2,3,4}}
%e A305857 {{1,2},{1,3},{1,4},{2,3,4}}
%e A305857 {{1,2,3},{1,2,4},{1,3,4},{2,3,4}}
%Y A305857 Cf. A001206, A006126, A051185, A261006, A283877, A304998, A305843, A305844, A305854, A305855, A305856.
%K A305857 nonn,more
%O A305857 0,2
%A A305857 _Gus Wiseman_, Jun 11 2018
%E A305857 a(6) from _Andrew Howroyd_, Aug 13 2019
%E A305857 a(7) from _Brendan McKay_, May 11 2020