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A130913
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Composite solutions to the equation phi(x)+sigma(x) = 2*reversal(x).
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1
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OFFSET
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1,1
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COMMENTS
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For a prime p we have phi(p)+sigma(p) = 2*reversal(p) iff p is a palindrome.
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LINKS
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EXAMPLE
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485700768 is in the sequence because 485700768 is composite and phi(485700768)+sigma(485700768) = 1734015168 = 2*867007584.
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MATHEMATICA
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Do[a=FromDigits[Reverse[IntegerDigits[n]]]; If[a>n&&EulerPhi[n]+ DivisorSigma[1, n]==2a, Print[n]], {n, 250000000}] (* Farideh Firoozbakht, Nov 26 2013 *)
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CROSSREFS
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KEYWORD
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hard,more,nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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