%I #13 Apr 22 2019 11:46:43
%S 1,3,9,33,123,513,2077,8759,37184,159508,688446,2993451,13082724
%N a(n) is the number of canonical polygons with 2n edges having 2-fold rotational symmetry.
%H Lars Blomberg, <a href="/A307454/a307454.pdf">Examples of canonical polygons with 2-fold rotational symmetry</a>
%Y Cf. A052436, A307387, A307391, A307426, A307454, A307455, A307456, A307519.
%K nonn,more
%O 2,2
%A _Lars Blomberg_, Apr 09 2019
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