A306175 Number of unrooted self-avoiding walks with n steps that can make turns from the set +-Pi/5, +-3*Pi/5.

1, 2, 6, 19, 66, 229, 831, 2991, 10859, 39173, 141631, 510079, 1835583, 6586932, 23614821, 84492315, 302014619, 1077860479, 3843695976, 13690026688

Offset: 1

Author

Hugo Pfoertner, Jun 23 2018

Keywords

• nonn
• walk
• more

Comments

The turning angles are those of the regular pentagon, 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 <= 5.

Crossrefs

Cf. A266925, A037245, A151541, A306177, A306178, A306179, A306180, A306181, A306182, A316195.

Extensions

a(7)-a(9) from Hugo Pfoertner, Dec 23 2018

a(10)-a(20) from Bert Dobbelaere, May 15 2025