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 A387068 #9 Aug 18 2025 00:39:26 %S A387068 1,3,31,1831,462638,243066565 %N A387068 Number of equivalence classes (up to homeomorphism) of finite, connected ribbon graphs that have an embedding in an orientable surface of genus n which minimally separates the surface of genus n (that is, no proper subset of the embedding separates the genus n surface) but not the surface of genus n-1. %C A387068 n is called the least separating genus. %C A387068 These numbers are larger than those of A387067, because different embeddings of the same graph are counted separately. For instance, there is a ribbon graph for the bouquet of 3 circles with least separating genus 1 and a different embedding with least separating genus 2. %D A387068 C. N. Aagaard and J. J. P. Veerman, Classification of Minimal Separating Sets of Low Genus Surfaces, Topology and its Applications, Accepted, 2025. %e A387068 For genus 0: thickened circle. %e A387068 For genus 1: thickened versions of a bouquet of 2 circles, bouquet of 3 circles, 4-fold multi-edge. %Y A387068 Cf. A384639, A387066, A387067. %K A387068 nonn,more %O A387068 0,2 %A A387068 _J. J. P. Veerman_, Aug 15 2025