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A053634
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a(n) = Sum_{ d divides n } phi(d)*2^(n/d)/(2n).
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6
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2, 3, 4, 7, 10, 18, 30, 54, 94, 176, 316, 591, 1096, 2058, 3856, 7301, 13798, 26244, 49940, 95373, 182362, 349626, 671092, 1290714, 2485534, 4793790, 9256396, 17896284, 34636834, 67109898, 130150588, 252647064, 490853416, 954440950
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OFFSET
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3,1
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COMMENTS
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Offset is 3 because a(2) is 3/2, not an integer. - Michel Marcus, Sep 11 2013
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LINKS
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FORMULA
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MATHEMATICA
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a[n_] := DivisorSum[n, EulerPhi[#]*2^(n/#)&]/(2n); Table[a[n], {n, 3, 36}] (* Jean-François Alcover, Dec 07 2015 *)
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PROG
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(PARI) a(n) = sumdiv (n, d, eulerphi(d)*2^(n/d)/(2*n)); \\ Michel Marcus, Sep 11 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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