A306181 Number of unrooted self-avoiding walks with n steps that can make turns from the set +-Pi/11, +-3*Pi/11, +-5*Pi/11, +-7*Pi/11, +-9*Pi/11.

1, 5, 28, 235, 1970, 17201, 149420, 1295637, 11178026, 96047288, 822418731, 7020762655

Offset: 1

Author

Hugo Pfoertner, Jun 23 2018

Keywords

• nonn
• walk
• more

Comments

The turning angles are those of the regular 11-gon, with one vertex corresponding to the forbidden U-turn. The path may neither intersect nor touch itself anywhere.

Links

• Contest Organizers, Al Zimmermann's Programming Contests - Snakes on a Plane, Fall 2006.
• Hugo Pfoertner, Illustration of walks of lengths <= 3.

Crossrefs

Cf. A266925, A037245, A306175, A151541, A306177, A306178, A306179, A306180, A306182.

Extensions

a(7)-a(12) from Bert Dobbelaere, May 15 2025