OFFSET
0,3
COMMENTS
Also, the number of 4 X n {-1,0,1} matrices with all rows and columns summing to zero up to permutations of rows.
EXAMPLE
The a(2) = 3 matrices are:
[1 1] [2 0] [2 0]
[1 1] [1 1] [2 0]
[1 1] [1 1] [0 2]
[1 1] [0 2] [0 2]
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Oct 15 2024
STATUS
approved