OFFSET
1,3
COMMENTS
An even digit turns the pencil 0 degrees to the right, then advances 1 unit; an odd digit turns the pencil 90 degrees to the right, then advances 1 unit.
EXAMPLE
The pencil points towards the East before the start. The 0 doesn't change its orientation and a 1-unit line directed towards the East is traced. As 1 is odd, the pencil turns 90 degrees towards the South and a 1-unit line is traced. As 3 is odd, the pencil turns 90 degrees towards the West and a 1-unit line is traced. As 2 is even, the pencil doesn't change its orientation (towards the West) and a 1-unit line is traced. As 5 is odd, the pencil turns 90 degrees towards the North and a 1-unit line is traced. As 4 is even, the pencil doesn't change its orientation (towards the North) and a 1-unit line is traced. Etc.
When it comes to a(11) = 20, the pencil reads 2 (even), doesn't change its orientation and advances 1 square, then reads 0 (even), doesn't change its orientation and advances 1 square again.
When it comes to a(12) = 10, the pencil reads 1 (odd), turns to the right and advances 1 square, then reads 0 (even), doesn't change its orientation and advances 1 square. Etc.
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Eric Angelini and Carole Dubois, Jun 04 2021
STATUS
approved