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

Offset

1,2

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

Table of n, a(n) for n=1..9.

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.

Sequence in context: A150084 A275755 A150085 * A266466 A005654 A150086

Adjacent sequences: A306172 A306173 A306174 * A306176 A306177 A306178

Keyword

nonn,walk,more

Author

Hugo Pfoertner, Jun 23 2018

Extensions

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

Status

approved