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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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FORMULA
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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):
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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