A306177 Number of unrooted self-avoiding walks with n steps that can make turns from the set +-Pi/7, +-3*Pi/7, +-5*Pi/7.

1, 3, 11, 55, 275, 1444, 7609, 40220, 212051, 1114206, 5840287, 30521627, 159166728, 828130291, 4301636648

Offset: 1

Author

Hugo Pfoertner, Jun 23 2018

Keywords

• nonn
• walk
• more

Comments

The turning angles are those of the regular heptagon, 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 <= 4.

Crossrefs

Cf. A266925, A037245, A306175, A151541, A306178, A306179, A306180, A306181, A306182.

Extensions

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