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A184265
Number of distinct n X 3 toroidal binary arrays.
2
4, 14, 64, 352, 2192, 14624, 99880, 699252, 4971184, 35792568, 260301176, 1908882592, 14096303344, 104715443852, 781874941184, 5864062367252, 44152937528384, 333599974922264, 2528336632928152, 19215358428046176, 146402730743992960, 1117984489446008100
OFFSET
1,1
LINKS
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) ~ 8^n / (3*n). - Vaclav Kotesovec, Sep 04 2014
MAPLE
with(numtheory):
a:= n-> add(add(phi(c)*phi(d) *2^(3*n/ilcm(c, d)),
d=divisors(n)), c=[1, 3])/(3*n):
seq(a(n), n=1..30); # Alois P. Heinz, Aug 25 2012
CROSSREFS
Column 3 of A184271.
Sequence in context: A356004 A154407 A222467 * A020041 A081891 A119857
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 10 2011
EXTENSIONS
More terms from Alois P. Heinz, Aug 25 2012
STATUS
approved