OFFSET
1,2
COMMENTS
Here a "mod n square grid graph" is a n X n graph with wrapping allowed, e.g., a path can make a 1 unit step between the left and the right edge (same row) or the top and the bottom edge (same column) of the graph.
Excludes 0 length paths; including them increases each term by 1.
EXAMPLE
a(2) = 4, all symmetric and count as 1 each both undirected and directed:
X--X X--+ X--+ X--+
| | |
X X--+ ..X +..
Nonsymmetric paths count as 2 each when directed, e.g.:
X--+--+ X>>+>>+ X<<+<<+
| -> v and ^
X X X
CROSSREFS
KEYWORD
nonn,walk,hard,more
AUTHOR
Charles L. Hohn, May 22 2026
STATUS
approved
