A085506 - OEIS

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A085506

Number of {-1,0,1} n X n matrices that have (real and) positive eigenvalues.

1, 5, 133, 18905 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	LINKS	`B. D. McKay, F. E. Oggier, G. F. Royle, N. J. A. Sloane, I. M. Wanless and H. S. Wilf, Acyclic digraphs and eigenvalues of (0,1)-matrices, J. Integer Sequences, 7 (2004), #04.3.3.` `B. D. McKay, F. E. Oggier, G. F. Royle, N. J. A. Sloane, I. M. Wanless and H. S. Wilf, Acyclic digraphs and eigenvalues of (0,1)-matrices` `Eric Weisstein's World of Mathematics, Positive Definite Matrix` `Index entries for sequences related to binary matrices`
	CROSSREFS	`Sequence in context: A152794 A053517 A114474 * A132508 A159355 A184577` `Adjacent sequences: A085503 A085504 A085505 * A085507 A085508 A085509`
	KEYWORD	`nonn,more`
	AUTHOR	`Eric Weisstein (eric(AT)weisstein.com), Jul 02, 2003`
	EXTENSIONS	`Offset corrected. - Max Alekseyev (maxale(AT)gmail.com), Oct 18 2008`

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Last modified February 14 22:52 EST 2012. Contains 205685 sequences.