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%I #4 Dec 18 2015 18:17:17
%S 54,20,3552,11364,2742240,56271108,23882769984,990946452040,
%T 760348893638560
%N Number of n X n arrays of squares of integers, symmetric about both diagonal and antidiagonal, with all rows summing to 21.
%K nonn
%O 4,1
%A _R. H. Hardin_ Feb 09 2009