OFFSET
0,2
COMMENTS
a(n) is the number of 2n X 2n symmetric binary matrices with n ones in every row and column.
FORMULA
a(n) = A333157(2*n, n).
a(n) = A213793(2*n). - Andrew Howroyd, Apr 08 2020
EXAMPLE
The a(1) = 2 matrices are:
[ 1 -1] [-1 1]
[-1 1] [ 1 -1]
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Mar 11 2020
STATUS
approved