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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
CROSSREFS
Sequence in context: A098401 A355363 A011544 * A214363 A204821 A365156
KEYWORD
nonn,more,nice
AUTHOR
Max Alekseyev, Jan 16 2007
STATUS
approved

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Last modified March 28 22:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)