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A109043
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a(n) = lcm(n,2).
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20
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0, 2, 2, 6, 4, 10, 6, 14, 8, 18, 10, 22, 12, 26, 14, 30, 16, 34, 18, 38, 20, 42, 22, 46, 24, 50, 26, 54, 28, 58, 30, 62, 32, 66, 34, 70, 36, 74, 38, 78, 40, 82, 42, 86, 44, 90, 46, 94, 48, 98, 50, 102, 52, 106, 54, 110, 56, 114, 58, 118, 60, 122, 62, 126, 64, 130, 66, 134
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refs;
listen;
history;
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internal format)
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OFFSET
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0,2
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COMMENTS
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Exponent of the dihedral group D(2n) = <x, y | x^n = y^2 = 1, yxy = x^-1>. - Arkadiusz Wesolowski, Sep 10 2013
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LINKS
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FORMULA
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a(n) = n*2 / gcd(n, 2).
G.f.: 2*x(1+x+x^2)/((1-x)^2*(1+x)^2). (End)
Sum_{k=1..n} a(k) ~ (3/4) * n^2. - Amiram Eldar, Nov 26 2022
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MATHEMATICA
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PROG
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(Haskell)
a109043 = (lcm 2)
a109043_list = zipWith (*) [0..] a000034_list
(Magma) [0, 2, 2] cat [Exponent(DihedralGroup(n)) : n in [3..65]] // Arkadiusz Wesolowski, Sep 10 2013
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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