OFFSET
1,5
COMMENTS
a(n) is also the number of walks of length 4*n on a 2D lattice with the properties that: it turns 90 degrees after every step of length 1, it is a closed loop (i.e., it ends where it started) and it never crosses itself.
In A266549, the walks are allowed to continue straight ahead. - Pontus von Brömssen, May 06 2025
LINKS
EXAMPLE
a(2) = 0 because there are no lakes with 16 cells.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Nathaniel Johnston, Feb 06 2009
EXTENSIONS
a(11) and a(12) added by Nathaniel Johnston, Mar 09 2009
STATUS
approved
