%I #11 Jul 03 2018 04:18:08
%S 0,0,2,1,18,45,441
%N Number of self-avoiding polygons with perimeter 2*n and sides = 1 that have vertex angles from the set +-Pi/5, +-3*Pi/5, not counting rotations and reflections as distinct.
%C Holes are excluded, i.e., the boundary path may nowhere touch or intersect itself.
%H Contest Organizers, <a href="http://www.recmath.org/contest/Snakes/index.php">Al Zimmermann's Programming Contests - Snakes on a Plane</a>, Fall 2006.
%H Hugo Pfoertner, <a href="http://www.randomwalk.de/sequences/a316195.htm">Illustration of polygons of perimeter <= 14</a>.
%Y Cf. A306175, A258206, A266549, A284869.
%K nonn,walk,more
%O 1,3
%A _Hugo Pfoertner_, Jun 26 2018