OFFSET
0,2
COMMENTS
See A210000 for a guide to related sequences.
LINKS
Chai Wah Wu, Table of n, a(n) for n = 0..10000
EXAMPLE
a(1) counts these matrices (in reduced notation):
(-1,-1,1,-1), (-1,1,-1,-1), (1,-1,1,1), (1,1,-1,1)
MATHEMATICA
(See the Mathematica section at A209981.)
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, Mar 17 2012
STATUS
approved