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Number of unrooted self-avoiding walks with n steps that can make turns from the set 0, +-Pi/5, +-2*Pi/5, +-3*Pi/5, +-4*Pi/5.
10

%I #7 Jun 25 2018 12:46:22

%S 1,5,23,169,1233,9551

%N Number of unrooted self-avoiding walks with n steps that can make turns from the set 0, +-Pi/5, +-2*Pi/5, +-3*Pi/5, +-4*Pi/5.

%C The turning angles are those of the regular decagon, with one vertex corresponding to the forbidden U-turn. The path may neither intersect nor touch itself anywhere.

%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/a306180.htm">Illustration of walks of lengths <= 3</a>.

%Y Cf. A266925, A037245, A306175, A151541, A306177, A306178, A306179, A306181, A306182.

%K nonn,walk,more

%O 1,2

%A _Hugo Pfoertner_, Jun 23 2018