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A184264
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Number of distinct n X 2 toroidal binary arrays.
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2
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3, 7, 14, 40, 108, 362, 1182, 4150, 14602, 52588, 190746, 699600, 2581428, 9588742, 35792568, 134223910, 505294128, 1908896442, 7233642930, 27487869472, 104715443852, 399822696082, 1529755490574, 5864063066500, 22517998808028, 86607689013412, 333599974893066
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OFFSET
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1,1
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LINKS
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Alois P. Heinz, Table of n, a(n) for n = 1..1000
S. N. Ethier, Counting toroidal binary arrays, arXiv preprint arXiv:1301.2352, 2013 and J. Int. Seq. 16 (2013) #13.4.7 .
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FORMULA
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a(n) ~ 2^(2*n-1) / n. - Vaclav Kotesovec, Sep 04 2014
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MAPLE
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with(numtheory):
a:= n-> add(add(phi(c)*phi(d) *2^(2*n/ilcm(c, d)),
d=divisors(n)), c=[1, 2])/(2*n):
seq(a(n), n=1..30); # Alois P. Heinz, Aug 25 2012
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CROSSREFS
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Column 2 of A184271.
Sequence in context: A079939 A147006 A146936 * A298913 A266019 A146155
Adjacent sequences: A184261 A184262 A184263 * A184265 A184266 A184267
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Jan 10 2011
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EXTENSIONS
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More terms from Alois P. Heinz, Aug 25 2012
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STATUS
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approved
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