OFFSET
1,2
COMMENTS
The maximum possible number of unit squares is given by A331968(n).
Equivalently, a(n) is the number of maximum length paths without chords in the n X n grid graph. A path without chords is an induced subgraph that is a path.
For n > 1, a(n) is a multiple of 4 since a solution can have at most one symmetry considering rotations and reflections. - Andrew Howroyd, Feb 04 2020
LINKS
Eric Weisstein's World of Mathematics, Grid Graph
EXAMPLE
For n = 4 the number of snake-like polyominoes with 11 cells is 84.
CROSSREFS
KEYWORD
nonn,walk,hard,more
AUTHOR
Alain Goupil, Feb 03 2020
EXTENSIONS
a(15) from Andrew Howroyd, Feb 04 2020
a(16)-a(17) from Yi Yang, Oct 03 2022
STATUS
approved