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A087982
Maximal permanent of a nonsingular n X n (+1,-1)-matrix.
3
1, 0, 2, 8, 24, 128
OFFSET
1,3
COMMENTS
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).
This has been proved by Budrevich and Guterman. - Sergei Shteiner, Jan 21 2020
The maximal possible value for the permanent of a singular n X n (+1,-1)-matrix is obviously n!.
LINKS
Mikhail V. Budrevich, Alexander E. Guterman, Kräuter conjecture on permanents is true, arXiv:1810.04439 [math.CO], 2018.
Arnold R. Kräuter and Norbert Seifter, Some properties of the permanent of (1,-1)-matrices, Linear and Multilinear Algebra 15 (1984), 207-223.
Norbert Seifter, Upper bounds for permanents of (1,-1)-matrices, Israel J. Math. 48 (1984), 69-78.
Edward Tzu-Hsia Wang, On permanents of (1,-1)-matrices, Israel J. Math. 18 (1974), 353-361.
FORMULA
a(n) = A087981(n-1) for n >= 5. - Sergei Shteiner, Jan 20 2020
EXAMPLE
a(4) = 8 from the following matrix:
-1 +1 +1 +1
+1 +1 +1 +1
+1 -1 +1 -1
-1 +1 +1 -1
CROSSREFS
For n != 4 this is given by A087981. Cf. A087983.
Sequence in context: A052624 A272590 A361991 * A176475 A145238 A093458
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Oct 28 2003
EXTENSIONS
a(4) = 8 from W. Edwin Clark and Wouter Meeussen, a(5) = 24 and a(6) = 128 from Jaap Spies, Oct 29 2003
STATUS
approved