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A055631
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Sum of Euler's totient function phi of distinct primes dividing n.
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8
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0, 1, 2, 1, 4, 3, 6, 1, 2, 5, 10, 3, 12, 7, 6, 1, 16, 3, 18, 5, 8, 11, 22, 3, 4, 13, 2, 7, 28, 7, 30, 1, 12, 17, 10, 3, 36, 19, 14, 5, 40, 9, 42, 11, 6, 23, 46, 3, 6, 5, 18, 13, 52, 3, 14, 7, 20, 29, 58, 7, 60, 31, 8, 1, 16, 13, 66, 17, 24, 11, 70, 3, 72, 37, 6, 19, 16, 15, 78, 5, 2
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OFFSET
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1,3
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LINKS
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FORMULA
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If n = p^w, a power of prime, then a(n) = p-1; if n = 2p, then a(n) = p = n/2.
Additive with a(p^e) = p-1: a(10) = a(2*5) = a(2)+a(5) = (2-1)+(5-1) = 5; a(28) = a(2^2*7) = a(2^2)+a(7) = 1+6 = 7. - Vladeta Jovovic, Oct 23 2001
G.f.: Sum_{k>=1} (prime(k) - 1) * x^prime(k) / (1 - x^prime(k)). - Ilya Gutkovskiy, Aug 18 2021
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MAPLE
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with(numtheory); a := n -> add(f, f = map(phi, factorset(n)));
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MATHEMATICA
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Join[{0}, Table[Total[EulerPhi[Transpose[FactorInteger[n]][[1]]]], {n, 2, 90}]] (* Harvey P. Dale, Oct 29 2012 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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