%I A156431
%S A156431 1,0,2,0,12,0,90,0,810,0,8940,0,116760,0,1756860,0,29933820,0,569744280,
%T A156431 0,11981526480,0,275893362360,0,6903968231160,0,186558764792400,0,
%U A156431 5413973807642400
%N A156431 Number of nXn arrays of squares of integers, symmetric under 90 degree 
               rotation, with all rows summing to 2.
%Y A156431 Sequence in context: A053814 A095238 A167345 this_sequence A067994 A143246 
               A104014
%Y A156431 Adjacent sequences: A156428 A156429 A156430 this_sequence A156432 A156433 
               A156434
%K A156431 nonn
%O A156431 2,3
%A A156431 Ron Hardin (rhhardin(AT)att.net) Feb 09 2009