OFFSET
1,4
COMMENTS
If you allow going down on the first step you get two times a(n) for n > 1.
All symmetrical self-avoiding walks on a square board with odd length seem to have a 180-degree rotational symmetry, and all symmetrical self-avoiding walks on a square board with even length seem to have either vertically or horizontally reflection symmetry.
LINKS
EXAMPLE
The solutions for n=3 and n=4:
n=3: | n=4:
1 | 1 2
>>v | >>>v | >v>
v<< | v<<< | v<^<
>> | >>>v | v>v^
| <<< | >^>^
CROSSREFS
KEYWORD
nonn,walk,hard,nice
AUTHOR
S. Brunner, Feb 02 2020
EXTENSIONS
a(11)-a(20) from Andrew Howroyd, Feb 20 2020
a(21) from Andrew Howroyd, Oct 16 2024
STATUS
approved