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A161217
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a(n) = Sum_{d|n} phi(n/d)^2*2^(d+1).
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3
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0, 4, 12, 32, 56, 128, 192, 400, 640, 1232, 2304, 4496, 8608, 16960, 33456, 66304, 132096, 263168, 526320, 1049872, 2100352, 4196480, 8393904, 16779152, 33565952, 67111488, 134235840, 268441424, 536906720, 1073744960, 2147560704, 4294970896, 8590069760
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OFFSET
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0,2
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LINKS
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FORMULA
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MAPLE
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a:= proc(n) uses numtheory;
add(phi(n/d)^2*2^(d+1), d=divisors(n))
end:
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PROG
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(PARI) a(n) = if (n, sumdiv(n, d, eulerphi(n/d)^2*2^(d+1)), 0); \\ Michel Marcus, Jun 24 2021
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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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