# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a326215 Showing 1-1 of 1 %I A326215 #6 Jun 17 2019 21:47:20 %S A326215 0,2,0,4,20 %N A326215 Number of Hamiltonian unlabeled n-vertex graphs with loops. %C A326215 A graph is Hamiltonian if it contains a cycle passing through every vertex exactly once. %H A326215 Wikipedia, Hamiltonian path %H A326215 Gus Wiseman, Non-isomorphic representatives of the a(4) = 20 Hamiltonian graphs with loops. %e A326215 Non-isomorphic representatives of the a(3) = 4 edge-sets: %e A326215 {12,13,23} %e A326215 {12,13,23,33} %e A326215 {12,13,22,23,33} %e A326215 {11,12,13,22,23,33} %Y A326215 The labeled case is A326240. %Y A326215 The directed case is A326226 (with loops) or A326225 (without loops). %Y A326215 The case without loops A003216. %Y A326215 Cf. A000088, A006125, A057864, A283420, A326239. %K A326215 nonn,more %O A326215 0,2 %A A326215 _Gus Wiseman_, Jun 17 2019 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE