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%I #6 Jul 02 2018 20:27:14
%S 0,0,3,4,83,533,8329
%N Number of self-avoiding polygons with perimeter 2*n and sides = 1 that have vertex angles from the set +-Pi/7, +-3*Pi/7, +-5*Pi/7, not counting rotations and reflections as distinct.
%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/a316197.htm">Illustration of polygons of perimeter <= 12</a>.
%Y Cf. A306177, A258206, A266549, A284869, A316195.
%K nonn,walk,more
%O 1,3
%A _Hugo Pfoertner_, Jun 28 2018