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%I #4 Mar 30 2012 18:37:44
%S 1,3,10,39,121,405
%N Number of (-1,0,1) periodic irreducible matrices (with Tij=-Tji for i<j) up to sign change, transposition and row and column permutations.
%C The permutations of rows i anf j, followed by those of column i and j, preserve the property that (Tij=-Tji for i<j). The periods of the 405 6 X 6 matrices are: 11 times period 3, 94 times period 4, 71 times period 6 and 229 times period 12.
%H Wouter Meeussen, <a href="http://users.pandora.be/Wouter.Meeussen/PseudoAntiSymmetricMatrixPowers.nb">Periodic Matrices</a>
%e {{-1,-1,0,0,0,0},{1,1,-1,0,0,0},{0,1,-1,0,0,0},{0,0,0,-1,-1,0},{0,0,0,1,1,-1},{0,0,0,0,1,-1}} is one of the 6 by 6 matrices.
%t see link.
%Y Cf. A072148, A111485.
%K hard,nonn
%O 1,2
%A _Wouter Meeussen_, Nov 19 2005
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