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A121850
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Numbers n such that (phi(n) + sigma(n))/(rad(n))^2 is an integer, that is (phi(n) + sigma(n)) is divisible by every prime factor of n squared.
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0
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2, 588, 864, 2430, 7776, 27000, 55296, 69984, 82134, 215622, 432000, 497664, 629856, 675000, 862488, 1499136, 1749600, 2187000, 2667168, 3449952, 3538944, 4287500, 4312440, 4478976, 4563000, 5668704, 6912000, 10800000, 13045131
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..29.
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EXAMPLE
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For example, phi(588) = 168, sigma(588) = 1596, 588 = 2^2*3*7^2. The product of all prime divisors is 42, its square is 1764. Hence phi(588) + sigma(588), which is equal to 1764 is divisible by the square of each prime divisor of 588.
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MATHEMATICA
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Do[If[IntegerQ[(DivisorSigma[1, n] + EulerPhi[n])/(Times @@ Transpose[FactorInteger[n]][[1]])^2], Print[n]], {n, 2, 1000000}]
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CROSSREFS
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Cf. a(n) are numbers n such that A000010(n) + A000203(n) is divisible by A007947(n)^2. This sequence is similar to A097982.
Sequence in context: A129697 A214911 A203770 * A100011 A172892 A134796
Adjacent sequences: A121847 A121848 A121849 * A121851 A121852 A121853
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KEYWORD
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nonn
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AUTHOR
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Tanya Khovanova, Aug 30 2006
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EXTENSIONS
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a(16)-a(29) from Donovan Johnson, Feb 05 2010
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STATUS
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approved
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