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A145676 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. 2
1, 2, 49, 8419, 9162049 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..4.

EXAMPLE

Here are the 2 for the 1 X 1 case:

{{{0}}, {{1}}}

and the 49 for the 2 X 2 case:

{{{-1, -1}, {0, -1}}, {{-1, -1}, {0, 0}}, {{-1, -1}, {1, -1}}, {{-1, -1}, {1, 0}},

{{-1, 0}, {-1, -1}}, {{-1, 0}, {-1, 0}}, {{-1, 0}, {0, -1}}, {{-1, 0}, {0, 0}},

{{-1, 0}, {1, -1}}, {{-1, 0}, {1, 0}}, {{-1, 1}, {-1, -1}}, {{-1, 1}, {-1, 0}},

{{-1, 1}, {0, -1}}, {{-1, 1}, {0, 0}}, {{0, -1}, {0, -1}}, {{0, -1}, {0, 0}},

{{0, -1}, {0, 1}}, {{0, -1}, {1, -1}}, {{0, -1}, {1, 0}}, {{0, -1}, {1, 1}},

{{0, 0}, {-1, -1}}, {{0, 0}, {-1, 0}}, {{0, 0}, {-1, 1}}, {{0, 0}, {0, -1}},

{{0, 0}, {0, 0}}, {{0, 0}, {0, 1}}, {{0, 0}, {1, -1}}, {{0, 0}, {1, 0}},

{{0, 0}, {1, 1}}, {{0, 1}, {-1, -1}}, {{0, 1}, {-1, 0}}, {{0, 1}, {-1, 1}},

{{0, 1}, {0, -1}}, {{0, 1}, {0, 0}}, {{0, 1}, {0, 1}}, {{1, -1}, {0, 0}},

{{1, -1}, {0, 1}}, {{1, -1}, {1, 0}}, {{1, -1}, {1, 1}}, {{1, 0}, {-1, 0}},

{{1, 0}, {-1, 1}}, {{1, 0}, {0, 0}}, {{1, 0}, {0, 1}}, {{1, 0}, {1, 0}},

{{1, 0}, {1, 1}}, {{1, 1}, {-1, 0}}, {{1, 1}, {-1, 1}}, {{1, 1}, {0, 0}}, {{1, 1}, {0, 1}}}

CROSSREFS

Cf. A145675.

Sequence in context: A257742 A269839 A088067 * A291188 A225795 A027619

Adjacent sequences:  A145673 A145674 A145675 * A145677 A145678 A145679

KEYWORD

nonn

AUTHOR

Eric W. Weisstein, Mar 26 2009

EXTENSIONS

a(4) from Eric W. Weisstein, Mar 27 2009

STATUS

approved

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Last modified September 20 10:10 EDT 2019. Contains 327229 sequences. (Running on oeis4.)