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%I #3 Mar 31 2012 14:09:57
%S 1,3,73,12787,13698241
%N Number of n X n {0,-1,1}-matrices A such that permanent( |A| ) = | det A |, where |A| is obtained from A by taking the absolute value of each entry.
%C Also the number of n X n sign-nonsingular matrices (see reference for definition).
%D Brualdi, Richard A. and Shader, Bryan L., On sign-nonsingular matrices and the conversion of the permanent into the determinant, in Applied Geometry and Discrete Mathematics (The Victor Klee Festschrift), pp. 117-134, DIMACS Ser. Discrete Math. Theoret. Comput. Sci., 4, Amer. Math. Soc., Providence, RI, 1991.
%Y Cf. A145676.
%K nonn
%O 0,2
%A _N. J. A. Sloane_, Mar 26 2009
%E a(1)-a(4) computed by _Eric W. Weisstein_, Mar 26, 2009
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