%I A087982
%S A087982 1,0,2,8,24,128
%N A087982 Maximal permanent of a nonsingular n X n (+1,-1)-matrix.
%C A087982 It is conjectured by Kraeuter and Seifter that for n >= 5 the maximal 
               permanent of a nonsingular n X n (+1,-1)-matrix is attained by a 
               matrix with exactly n-1 -1's on the diagonal (compare A087981).
%C A087982 The maximal possible value for the permanent of a singular n X n (+1,
               -1)-matrix is obviously n!.
%D A087982 A. R. Kraeuter and N. Seifter, Some properties of the permanent of (1,
               -1)-matrices, Linear and Multilinear Algebra 15 (1984), 207-223.
%D A087982 N. Seifter, Upper bounds for permanents of (1,-1)-matrices, Israel J. 
               Math. 48 (1984), 69-78.
%D A087982 Edward Tzu-Hsia Wang, On permanents of (1,-1)-matrices, Israel J. Math. 
               18 (1974), 353-361.
%H A087982 <a href="Sindx_Mat.html#binmat">Index entries for sequences related to 
               binary matrices</a>
%e A087982 a(4) = 8 from the following matrix:
%e A087982 -1 +1 +1 +1
%e A087982 +1 +1 +1 +1
%e A087982 +1 -1 +1 -1
%e A087982 -1 +1 +1 -1
%Y A087982 The conjecture is that for n != 4 this is given by A087981. Cf. A087983.
%Y A087982 Sequence in context: A157005 A123775 A052624 this_sequence A145238 A093458 
               A088994
%Y A087982 Adjacent sequences: A087979 A087980 A087981 this_sequence A087983 A087984 
               A087985
%K A087982 nonn
%O A087982 1,3
%A A087982 N. J. A. Sloane (njas(AT)research.att.com), Oct 28 2003
%E A087982 a(4) = 8 from Edwin Clark and Wouter Meeussen, a(5) = 24 and a(6) = 128 
               from Jaap Spies, Oct 29 2003.