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A184264 Number of distinct n X 2 toroidal binary arrays. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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 .

FORMULA

a(n) ~ 2^(2*n-1) / n. - Vaclav Kotesovec, Sep 04 2014

MAPLE

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

CROSSREFS

Column 2 of A184271.

Sequence in context: A079939 A147006 A146936 * A298913 A266019 A146155

Adjacent sequences:  A184261 A184262 A184263 * A184265 A184266 A184267

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 10 2011

EXTENSIONS

More terms from Alois P. Heinz, Aug 25 2012

STATUS

approved

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Last modified June 18 23:16 EDT 2021. Contains 345125 sequences. (Running on oeis4.)