This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A145675 #5 Jun 29 2025 21:56:36
%S A145675 1,3,73,12787,13698241
%N A145675 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 A145675 Also the number of n X n sign-nonsingular matrices (see reference for definition).
%D A145675 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 A145675 Cf. A145676.
%K A145675 nonn
%O A145675 0,2
%A A145675 _N. J. A. Sloane_, Mar 26 2009
%E A145675 a(1)-a(4) computed by _Eric W. Weisstein_, Mar 26 2009