%I #5 Nov 25 2018 12:24:25
%S 1,1,9,17,309,1265,48927,435807,36527739,709448287,129684847323,
%T 5504589599263,2200548059561679,204460755826652731
%N Number of n X n integer matrices, symmetric under 90-degree rotation, with adjacent elements differing by no more than 1, counting matrices differing by a constant only once.
%K nonn
%O 1,3
%A _R. H. Hardin_, Aug 06 2008