A306182 Number of unrooted self-avoiding walks with n steps that can make turns from the set 0, +-Pi/6, +-2*Pi/6, +-3*Pi/6, +-4*Pi/6, +-5*Pi/6.

1, 6, 33, 306, 2765, 26290, 247737, 2332965, 21856232, 204019196, 1897940592, 17606864337

Offset: 1

Author

Hugo Pfoertner, Jun 23 2018

Keywords

• nonn
• walk
• more

Comments

The turning angles are those of the regular 12-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, A306181.

Extensions

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