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 A326222 #13 Mar 17 2024 12:53:30 %S A326222 1,0,2,12,157,5883,696803,255954536 %N A326222 Number of non-Hamiltonian unlabeled n-vertex digraphs (without loops). %C A326222 A digraph is Hamiltonian if it contains a directed cycle passing through every vertex exactly once. %H A326222 Gus Wiseman, <a href="/A326222/a326222_1.png">Non-isomorphic representatives of the a(3) = 12 non-Hamiltonian digraphs</a>. %F A326222 a(n) = A000273(n) - A326225(n). - _Pontus von Brömssen_, Mar 17 2024 %Y A326222 The labeled case is A326218 (without loops) or A326220 (with loops). %Y A326222 The undirected case (without loops) is A246446. %Y A326222 The case with loops is A326223. %Y A326222 Hamiltonian unlabeled digraphs are A326225 (without loops) or A003216 (with loops). %Y A326222 Cf. A000273, A000595, A002416, A003087, A053763, A326216, A326217, A326224, A326226. %K A326222 nonn,hard,more %O A326222 0,3 %A A326222 _Gus Wiseman_, Jun 15 2019 %E A326222 a(5)-a(7) (using A000273 and A326225) from _Pontus von Brömssen_, Mar 17 2024