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..210
FORMULA
Empirical: a(n) = 4*a(n-1) +9*a(n-2) -52*a(n-3) -16*a(n-4) +271*a(n-5) -86*a(n-6) -724*a(n-7) +435*a(n-8) +1052*a(n-9) -760*a(n-10) -817*a(n-11) +575*a(n-12) +320*a(n-13) -150*a(n-14) -60*a(n-15)
EXAMPLE
Some solutions for n=3
..1..0..1..0....2.-4.-1.-4....5.-1..5.-2....4..2..2..2....2..0..1..0
..0.-1..0.-1...-4..6.-1..6...-1.-3.-1.-2....2.-8..4.-8....0.-2..1.-2
..1..0..1..0...-1.-1.-4.-1....5.-1..5.-2....2..4..0..4....1..1..0..1
..0.-1..0.-1...-4..6.-1..6...-2.-2.-2.-1....2.-8..4.-8....0.-2..1.-2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin Apr 12 2012
STATUS
approved