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%I #25 Aug 02 2018 18:40:29
%S 1,2,96,86016,1321205760,335522845163520,1385295986380096143360,
%T 92239345887620476544860815360,98654363640526679389774053813465907200,
%U 1691558770638735027870457216848672340872423014400,464518059995994038184379206447729320401459864818351813427200
%N Number of invertible n X n matrices mod 4 (i.e., over the ring Z_4).
%H Geoffrey Critzer, <a href="https://esirc.emporia.edu/handle/123456789/3595">Combinatorics of Vector Spaces over Finite Fields</a>, Master's thesis, Emporia State University, 2018.
%H J. Overbey, W. Traves and J. Wojdylo, <a href="http://jeff.over.bz/papers/undergrad/on-the-keyspace-of-the-hill-cipher.pdf">On the Keyspace of the Hill Cipher</a>
%F a(n) = 4^(n^2) * Product_{k=1..n} (1 - 1/2^k).
%F a(n) = 2^(n^2) * A002884(n). - _Geoffrey Critzer_, Feb 04 2018
%t a(0) = 1. a[n_] := 4^(n^2)*Product[1 - 1/2^k, {k, 1, n} ]; Table[ a[n], {n, 0, 10} ]
%o (PARI) for(n=1,11,print(4^(n^2)*prod(k=1,n,(1-1/2^k))))
%Y Column k=4 of A316622.
%Y Cf. A053291.
%K nonn
%O 0,2
%A Dan Fux (dan.fux(AT)OpenGaia.com or danfux(AT)OpenGaia.com), Nov 14 2001
%E More terms from _Robert G. Wilson v_ and _Jason Earls_, Nov 16 2001
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