Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #4 Mar 31 2012 12:36:08
%S 49,9331,8583967,41906480269,1150080863229361,184765819216226770459
%N Number of (n+1)X(n+1) 0..6 arrays with diagonal zero and the i,j-th 2X2 subblock sum equal to the j,i-th 2X2 subblock sum
%C Column 6 of A187408
%e Some solutions for 4X4
%e ..0..0..0..2....0..0..3..0....0..0..0..5....0..0..3..0....0..0..0..4
%e ..3..0..5..0....2..0..4..1....2..0..6..2....5..0..3..5....3..0..6..1
%e ..2..0..0..3....3..2..0..0....0..4..0..5....0..1..0..0....1..2..0..4
%e ..3..2..6..0....3..0..3..0....5..4..5..0....5..5..2..0....4..4..5..0
%K nonn
%O 1,1
%A _R. H. Hardin_ Mar 09 2011