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 A296105 #24 Mar 17 2020 10:16:32
%S A296105 1,2,5,25,157,1325,14358,199763,3549001,80673244,2352747542,
%T A296105 88240542454,4261209044877,264988507673267,21207485269909946,
%U A296105 2182146922863398203
%N A296105 a(n) is the number of connected transitive relations over n unlabeled nodes.
%C A296105 Inverse Euler transform of A091073. Here "connected" means that it is possible to reach any vertex starting from any other vertex by traversing edges in some direction, i.e., not necessarily in the direction in which the edges point, as in weakly connected digraphs.
%e A296105 a(2) = 5 because there are five connected transitive relations up to isomorphism: a->b with no loops, a->b with a loop on a, a->b with a loop on b, a->b->a with no loops, and a->b->a with loops on both a and b.
%t A296105 A091073 = Cases[Import["https://oeis.org/A091073/b091073.txt", "Table"], {_, _}][[All, 2]];
%t A296105 (* EulerInvTransform is defined in A022562 *)
%t A296105 {1} ~Join~ EulerInvTransform[A091073 // Rest] (* Jean-François Alcover, Dec 29 2019, updated Mar 17 2020 *)
%Y A296105 Cf. A091073 (all unlabeled transitive relations). For the labeled case, see A245731 (connected labeled transitive relations) and A006905 (all labeled transitive relations).
%K A296105 nonn,more
%O A296105 0,2
%A A296105 _Daniele P. Morelli_, Dec 04 2017