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%I #12 May 01 2017 22:03:01
%S 1,3,45360,2615348736000,1938901255416373248000000,
%T 46499165848737652183499931018854400000000,
%U 76035233004283445109031520415161922110944103922401280000000000
%N Number of n X n matrices on n^2 distinct symbols modulo rotations and reflections.
%C Also the number of distinct adjacency matrices on the n X n grid graph P_n x P_n. - _Eric W. Weisstein_, May 01 2017
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/AdjacencyMatrix.html">Adjacency Matrix</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GridGraph.html">Grid Graph</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SquareMatrix.html">Square Matrix</a>
%F a(n) = (n^2)!/8, n>1. - _Vladeta Jovovic_, Aug 10 2003
%t Table[Piecewise[{{1, n == 1}}, (n^2)!/8], {n, 7}]
%Y Cf. A087074.
%K nonn,easy
%O 1,2
%A _Eric W. Weisstein_, Aug 08 2003
%E More terms from _Sam Alexander_, Feb 27 2004