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1, 2, 6, 8, 15, 30, 49, 96, 189, 360, 693, 1416, 2743, 5516, 10980, 21952, 43707, 87642, 174781, 349920, 699216, 1398804, 2796225, 5594112, 11184875, 22372376, 44739810, 89484080, 178956999, 357926040, 715827913, 1431677824, 2863313640
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Table[DivisorSum[n, (2^# - (-1)^#) EulerPhi[3 n/#] &]/6, {n, 33}] (* Michael De Vlieger, Dec 01 2019 *)
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PROG
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(PARI) a(n) = sumdiv(n, d, (2^d - (-1)^d)*eulerphi(3*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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