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0, 1, 1, 4, 5, 14, 21, 48, 87, 180, 341, 704, 1365, 2758, 5475, 10976, 21845, 43806, 87381, 174960, 349573, 699402, 1398101, 2797008, 5592425, 11186188, 22369797, 44742040, 89478485, 178962840, 357913941, 715838912, 1431656457, 2863333392, 5726623175, 11453291400, 22906492245, 45813071890
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OFFSET
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1,4
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LINKS
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MATHEMATICA
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Table[DivisorSum[n, (2^# + 2 (-1)^#) EulerPhi[n/#] &]/6, {n, 38}] (* Michael De Vlieger, Mar 18 2019 *)
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PROG
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(PARI) a(n) = sumdiv(n, d, (2^d + 2*(-1)^d)*eulerphi(n/d))/6; \\ Michel Marcus, Mar 16 2019
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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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