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) = 5*a(n-1) +10*a(n-2) -82*a(n-3) -10*a(n-4) +576*a(n-5) -286*a(n-6) -2266*a(n-7) +1807*a(n-8) +5476*a(n-9) -5310*a(n-10) -8379*a(n-11) +9038*a(n-12) +8059*a(n-13) -9334*a(n-14) -4671*a(n-15) +5778*a(n-16) +1496*a(n-17) -2024*a(n-18) -226*a(n-19) +356*a(n-20) +12*a(n-21) -24*a(n-22)
EXAMPLE
Some solutions for n=3
..0..1..0..0....0..2..1..2....2..1..2..1...-2..1..1..1...-3..1.-3..1
..1.-2..1.-1....2.-4..1.-4....1.-4..1.-4....1..0.-2..0....1..1..1..1
..0..1..0..0....1..1..2..1....2..1..2..1....1.-2..4.-2...-3..1.-3..1
..0.-1..0..0....2.-4..1.-4....1.-4..1.-4....1..0.-2..0....1..1..1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin Apr 07 2012
STATUS
approved