%I #8 Apr 08 2020 01:56:26
%S 1,1760,526443,34725760,932587453,13937940952,138198204339,
%T 1012226679296,5875958390949,28376054552968,118033137259563,
%U 433946033473016,1438074947544977,4362051703339832,12258717265789491,32233542519648928,79941392042719253,188248433874383736,423266982431567911
%N Number of 6 X 6 0..n symmetric arrays with all rows summing to 3*n.
%e Some solutions for n=4
%e ..2..4..0..4..0..2....2..4..3..3..0..0....2..1..3..0..2..4....2..0..2..3..1..4
%e ..4..1..2..4..0..1....4..3..3..1..0..1....1..2..4..3..0..2....0..4..3..3..1..1
%e ..0..2..3..0..4..3....3..3..3..2..0..1....3..4..1..2..0..2....2..3..3..0..3..1
%e ..4..4..0..2..0..2....3..1..2..0..4..2....0..3..2..3..3..1....3..3..0..0..3..3
%e ..0..0..4..0..4..4....0..0..0..4..4..4....2..0..0..3..4..3....1..1..3..3..2..2
%e ..2..1..3..2..4..0....0..1..1..2..4..4....4..2..2..1..3..0....4..1..1..3..2..1
%Y Row 6 of A213800.
%K nonn
%O 0,2
%A _R. H. Hardin_, Jun 20 2012
%E a(0)=1 prepended and terms a(12) and beyond from _Andrew Howroyd_, Apr 07 2020