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%I #19 Dec 23 2021 12:09:03
%S 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 9,14,10,14,16,11,11,16
%N Number of 2-self-hedrites with n vertices.
%C 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 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 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 Cf. A167156, A167157, A167158, A167159, A111361, A167228, A167229.
%K nonn,more
%O 2,3
%A _Jonathan Vos Post_, Oct 30 2009
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