Problem 208

Robot Walks

A robot moves in a series of one-fifth circular arcs (72°), with a free choice of a clockwise or an anticlockwise arc for each step, but no turning on the spot.

One of 70932 possible closed paths of 25 arcs starting northward is

Given that the robot starts facing North, how many journeys of 70
arcs in length can it take that return it, after the final arc, to its
starting position?

(Any arc may be traversed multiple times.)

**
These problems are part of
Project Euler
and are licensed under
CC BY-NC-SA 2.0 UK
**