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Number of self-avoiding polygons with perimeter 2*n and sides = 1 that have vertex angles from the set +-Pi/11, +-3*Pi/11, +-5*Pi/11, +-7*Pi/11, +-9*Pi/11, not counting rotations and reflections as distinct.
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%I #7 Jul 07 2018 19:29:44

%S 0,0,8,19,720,10578

%N Number of self-avoiding polygons with perimeter 2*n and sides = 1 that have vertex angles from the set +-Pi/11, +-3*Pi/11, +-5*Pi/11, +-7*Pi/11, +-9*Pi/11, 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/a316201.htm">Illustration of polygons of perimeter <= 10</a>.

%Y Cf. A258206, A266549, A284869, A306181, A316192, A316195, A316197, A316198, A316199, A316200.

%K nonn,more

%O 1,3

%A _Hugo Pfoertner_, Jul 07 2018