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 A305935 #16 Aug 12 2019 23:08:21
%S A305935 1,0,1,12,809,1146800,899927167353,291136684655893185321964,
%T A305935 14704020783497694096988185391720223222562121969,
%U A305935 12553242487939982849962414795232892198542733492886483991398790450208264017757788101836749760
%N A305935 Number of labeled spanning intersecting set-systems on n vertices with no singletons.
%C A305935 An intersecting set-system S is a finite set of finite nonempty sets (edges), any two of which have a nonempty intersection. S is spanning if every vertex is contained in some edge. A singleton is an edge containing only one vertex.
%F A305935 a(n) = A305843(n) - n * A003465(n-1).
%F A305935 Inverse binomial transform of A306000. - _Andrew Howroyd_, Aug 12 2019
%e A305935 The a(3) = 12 spanning intersecting set-systems with no singletons:
%e A305935 {{1,2,3}}
%e A305935 {{1,2},{1,3}}
%e A305935 {{1,2},{2,3}}
%e A305935 {{1,3},{2,3}}
%e A305935 {{1,2},{1,2,3}}
%e A305935 {{1,3},{1,2,3}}
%e A305935 {{2,3},{1,2,3}}
%e A305935 {{1,2},{1,3},{2,3}}
%e A305935 {{1,2},{1,3},{1,2,3}}
%e A305935 {{1,2},{2,3},{1,2,3}}
%e A305935 {{1,3},{2,3},{1,2,3}}
%e A305935 {{1,2},{1,3},{2,3},{1,2,3}}
%Y A305935 Cf. A001206, A006126, A051185, A048143, A058891, A305001, A305843, A305844, A305854-A305857, A305999, A306000, A306001, A306008.
%K A305935 nonn
%O A305935 0,4
%A A305935 _Gus Wiseman_, Jun 15 2018
%E A305935 a(6)-a(8) from _Giovanni Resta_, Jun 20 2018
%E A305935 a(9) from _Andrew Howroyd_, Aug 12 2019