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A127503 Number of n X n matrices A with 1's on the main diagonal and -1's and 0's elsewhere such that A + A' has only 0's and -1's off the main diagonal and is positive semi-definite. 2
1, 3, 27, 281, 3945, 70635, 1437555, 30357425, 628337745 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For number of different values of A + A' see A084553.

LINKS

Table of n, a(n) for n=1..9.

CROSSREFS

Cf. A085657, A085658, A080858, A083029, A038379, A127502.

Sequence in context: A275998 A098401 A011544 * A214363 A204821 A200903

Adjacent sequences:  A127500 A127501 A127502 * A127504 A127505 A127506

KEYWORD

nonn,more,nice

AUTHOR

Max Alekseyev, Jan 16 2007

STATUS

approved

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Last modified July 25 22:38 EDT 2021. Contains 346294 sequences. (Running on oeis4.)