OFFSET
1,2
COMMENTS
For n > 1, a(n) is the number of connected edge covers in the n X n grid graph.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..15
Eric Weisstein's World of Mathematics, Grid Graph
EXAMPLE
The a(2) = 5 connected spanning subgraphs are the following subgraphs and their rotations and reflections.
o---o o---o
| | |
o---o o---o
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Jan 28 2023
STATUS
approved