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 A305856 #14 Apr 28 2025 08:46:15
%S A305856 1,2,4,14,124,14992,1289845584
%N A305856 Number of unlabeled intersecting set-systems on up to n vertices.
%C A305856 An intersecting set-system is a finite set of finite nonempty sets (edges), any two of which have a nonempty intersection.
%e A305856 Non-isomorphic representatives of the a(3) = 14 intersecting set-systems:
%e A305856 {}
%e A305856 {{1}}
%e A305856 {{1,2}}
%e A305856 {{1,2,3}}
%e A305856 {{2},{1,2}}
%e A305856 {{3},{1,2,3}}
%e A305856 {{1,3},{2,3}}
%e A305856 {{2,3},{1,2,3}}
%e A305856 {{3},{1,3},{2,3}}
%e A305856 {{3},{2,3},{1,2,3}}
%e A305856 {{1,2},{1,3},{2,3}}
%e A305856 {{1,3},{2,3},{1,2,3}}
%e A305856 {{3},{1,3},{2,3},{1,2,3}}
%e A305856 {{1,2},{1,3},{2,3},{1,2,3}}
%Y A305856 Cf. A001206, A006126, A051185, A261006, A283877, A304982, A304996, A304998, A305843, A305844, A305854-A305857.
%K A305856 nonn,more
%O A305856 0,2
%A A305856 _Gus Wiseman_, Jun 11 2018
%E A305856 a(5) from _Andrew Howroyd_, Aug 12 2019
%E A305856 a(6) from _Bert Dobbelaere_, Apr 28 2025