A118997 - OEIS

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A118997

Number of real n X n symmetric (+1,-1) matrices with negative determinant.

1, 4, 16, 80, 8448, 907904, 81949952 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	FORMULA	`a(2n+1) = A118994(2n+1) [From Max Alekseyev (maxale(AT)gmail.com), May 08 2009]`
	CROSSREFS	`Cf. A118999, A118994.` `Sequence in context: A020080 A003471 A002777 * A001257 A133053 A110378` `Adjacent sequences: A118994 A118995 A118996 * A118998 A118999 A119000`
	KEYWORD	`nonn,more`
	AUTHOR	`Giovanni Resta (g.resta(AT)iit.cnr.it), May 08 2006`

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Last modified February 15 17:13 EST 2012. Contains 205828 sequences.