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A114930
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Numbers n such that phi(n)=2*reversal(n).
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3
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OFFSET
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1,1
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COMMENTS
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If m>1 and p=3*10^m+7 is prime then 90*p is in the sequence because phi(90*p)=phi(90)*phi(p)=24*(3*10^m+6)=2*(36*10^m+72) =2*reversal(27*10^m+63)=2*reversal(9*p)=2*reversal(90*p). Note that 30 divides all known terms of this sequence. Next term is greater than 11*10^7.
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LINKS
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EXAMPLE
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637062480 is a term because phi(637062480) = 2*84260736 = 2*reversal(637062480).
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MATHEMATICA
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Do[If[EulerPhi[n]==2*FromDigits[Reverse[IntegerDigits[n]]], Print[n]], {n, 110000000}]
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CROSSREFS
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KEYWORD
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nonn,base,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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