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 A326225 #11 Jun 17 2019 03:33:01
%S A326225 0,1,1,4,61,3725,844141,626078904
%N A326225 Number of Hamiltonian unlabeled n-vertex digraphs (without loops).
%C A326225 A digraph is Hamiltonian if it contains a directed cycle passing through every vertex exactly once.
%H A326225 Sean A. Irvine, <a href="/A326225/a326225.txt">Non-isomorphic representatives of the a(5) = 3725 non-Hamiltonian digraphs (without loops)</a>
%H A326225 Gus Wiseman, <a href="/A326225/a326225.png">Non-isomorphic representatives of the a(4) = 61 non-Hamiltonian digraphs (without loops)</a>
%e A326225 Non-isomorphic representatives of the a(3) = 4 digraph edge-sets:
%e A326225 {12,23,31}
%e A326225 {12,13,21,32}
%e A326225 {12,13,21,23,31}
%e A326225 {12,13,21,23,31,32}
%Y A326225 The labeled case is A326219.
%Y A326225 The case with loops is A326226.
%Y A326225 The undirected case is A003216.
%Y A326225 Non-Hamiltonian unlabeled digraphs (without loops) are A326222.
%Y A326225 Cf. A000595, A002416, A003087, A003216, A053763, A246446, A326204, A326218, A326223.
%K A326225 nonn,hard,more
%O A326225 0,4
%A A326225 _Gus Wiseman_, Jun 15 2019
%E A326225 a(5)-a(7) from _Sean A. Irvine_, Jun 16 2019