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A056989
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Number of nonsingular n X n (-1,0,1)-matrices (over the reals).
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6
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OFFSET
| 1,1
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LINKS
| Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
Index entries for sequences related to binary matrices
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FORMULA
| It would be nice to have an estimate for the asymptotic rate of growth.
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EXAMPLE
| a(1) = 2: [1], [ -1].
a(2) = 48: There are 8 choices for the first column, u (say) and then the 2nd column can be anything except 0, u, -u, so 6 choices, giving a total of 8*6 = 48.
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CROSSREFS
| Cf. A055165, A053290, A056990; A055165, A002884, A046747.
Sequence in context: A002820 A196448 A053290 * A090770 A081960 A123742
Adjacent sequences: A056986 A056987 A056988 * A056990 A056991 A056992
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KEYWORD
| nonn,nice,more
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AUTHOR
| Eric Weisstein (eric(AT)weisstein.com)
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EXTENSIONS
| a(4) from Winston C. Yang (winston(AT)cs.wisc.edu), Aug 27 2000
Entry revised by N. J. A. Sloane (njas(AT)research.att.com), Jan 02 2007
a(5) from Giovanni Resta (g.resta(AT)iit.cnr.it), Feb 20 2009
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