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

Offset

1,2

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

Table of n, a(n) for n=1..6.

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.

Sequence in context: A365961 A103468 A192944 * A330515 A330534 A366182

Adjacent sequences: A306176 A306177 A306178 * A306180 A306181 A306182

Keyword

nonn,walk,more

Author

Hugo Pfoertner, Jun 23 2018

Status

approved