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A306899
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a(n) = Sum_{d|n} (2^d - (-1)^d)*phi(3*n/d).
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3
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6, 12, 36, 48, 90, 180, 294, 576, 1134, 2160, 4158, 8496, 16458, 33096, 65880, 131712, 262242, 525852, 1048686, 2099520, 4195296, 8392824, 16777350, 33564672, 67109250, 134234256, 268438860, 536904480, 1073741994, 2147556240, 4294967478, 8590066944
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OFFSET
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1,1
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LINKS
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MAPLE
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MATHEMATICA
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Table[DivisorSum[n, (2^# - (-1)^#) EulerPhi[3 n/#] &], {n, 10^4}] (* Michael De Vlieger, Mar 18 2019 *)
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PROG
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(PARI) a(n) = sumdiv(n, d, (2^d - (-1)^d)*eulerphi(3*n/d)); \\ 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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