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 A167227 #19 Dec 23 2021 12:09:03 %S A167227 1,1,2,2,3,3,3,3,5,4,4,6,5,5,8,5,6,8,6,8,10,7,7,10,10,8,12,10,9,14,9, %T A167227 9,14,10,14,16,11,11,16 %N A167227 Number of 2-self-hedrites with n vertices. %C A167227 A 2-self-hedrite is a self-dual plane multigraph such that each its face has 4 sides except for 2 faces with 2 sides. - _Andrey Zabolotskiy_, Dec 16 2021 %H A167227 Mathieu Dutour Sikiric and Michel Deza, <a href="https://arxiv.org/abs/0910.5323">4-regular and self-dual analogs of fullerenes</a>, arXiv:0910.5323 [math.GT], 2009. %F A167227 It appears that a(n+1) = A167156(2*n) - A167156(n) [discovered using Sequence Machine]. An equivalent assertion is that if a plane multigraph and its dual both have only 4-gonal faces except for 2 2-gonal ones, then they are isomorphic. - _Andrey Zabolotskiy_, Dec 16 2021 %Y A167227 Cf. A167156, A167157, A167158, A167159, A111361, A167228, A167229. %K A167227 nonn,more %O A167227 2,3 %A A167227 _Jonathan Vos Post_, Oct 30 2009