A306179 Number of unrooted self-avoiding walks with n steps that can make turns from the set +-Pi/9, +-3*Pi/9, +-5*Pi/9, +-7*Pi/9.

1, 4, 19, 128, 861, 6051, 42475, 297993, 2081607, 14485077, 100475175, 694838429, 4793805002

Offset: 1

Author

Hugo Pfoertner, Jun 23 2018

Keywords

• nonn
• walk
• more

Comments

The turning angles are those of the regular nonagon, 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, A306180, A306181, A306182.

Extensions

a(7)-a(13) from Bert Dobbelaere, May 15 2025