OFFSET
1,1
COMMENTS
Symmetry and 2X2 block sums zero implies that the diagonal x(i,i) are equal modulo 2 and x(i,j)=(x(i,i)+x(j,j))/2*(-1)^(i-j)
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..33
EXAMPLE
Some solutions for n=3
.-8..4..1..0...-3.-3.-3..0....8.-9..7.-5...-3.-3.-1..2...-2..6.-1.-1
..4..0.-5..4...-3..9.-3..6...-9.10.-8..6...-3..9.-5..4....6-10..5.-3
..1.-5.10.-9...-3.-3.-3..0....7.-8..6.-4...-1.-5..1..0...-1..5..0.-2
..0..4.-9..8....0..6..0..3...-5..6.-4..2....2..4..0.-1...-1.-3.-2..4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin Apr 20 2012
STATUS
approved