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A065128
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Number of invertible n X n matrices mod 4 (i.e. over the ring Z_4).
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3
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1, 2, 96, 86016, 1321205760, 335522845163520, 1385295986380096143360, 92239345887620476544860815360, 98654363640526679389774053813465907200, 1691558770638735027870457216848672340872423014400
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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LINKS
| J. Overbey, W. Traves and J. Wojdylo, On the Keyspace of the Hill Cipher
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FORMULA
| a(n) = 4^(n^2) * product k=1..n (1 - 1/2^k)
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MATHEMATICA
| a(0) = 1. a[n_] := 4^(n^2)*Product[1 - 1/2^k, {k, 1, n} ]; Table[ a[n], {n, 0, 10} ]
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PROG
| (PARI) for(n=1, 11, print(4^(n^2)*prod(k=1, n, (1-1/2^k))))
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CROSSREFS
| Cf. A053291.
Sequence in context: A123115 A119696 A064069 * A122222 A036980 A168442
Adjacent sequences: A065125 A065126 A065127 * A065129 A065130 A065131
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KEYWORD
| nonn
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AUTHOR
| Dan Fux (dan.fux(AT)OpenGaia.com or danfux(AT)OpenGaia.com), Nov 14 2001
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com) and Jason Earls (zevi_35711(AT)yahoo.com), Nov 16 2001
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