OFFSET
0,2
EXAMPLE
The 14 matrices counted by a(1) are as follows:
...
1 0...-1 0...-1 -1...-1 0...-1 0...-1 0...-1 1
0 1... 0 -1...0 1...-1 1....0 1 ...1 1... 0 1
...
0 -1...0 1...1 -1... 1 0....1 0....1 0....1 1
-1 0...1 0...0 -1...-1 -1...0 -1...1 -1...0 1
MATHEMATICA
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, Apr 09 2012
EXTENSIONS
Offset corrected by Pontus von Brömssen, Jan 22 2020
STATUS
approved