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A178326
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Numbers n such that n is the mean value of phi(n) and reversal(n).
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0
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OFFSET
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1,2
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COMMENTS
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If p=5*10^m-1 is prime then n=6*p is in the sequence (the proof is easy).
If p=1/111*(10^(3m+3)-1)-5*10^(3m) is prime then n=12*p is in the sequence. For m = 3,47,75,203,1259 ... p is prime. - Farideh Firoozbakht, Oct 04 2013
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LINKS
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EXAMPLE
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(1/2)*(phi(25524)+reversal(25524)) = (1/2)*(8496+42552) = 25524, so 25524 is in the sequence.
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MATHEMATICA
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r[n_]:=FromDigits[Reverse[IntegerDigits[n]]];
Do[If[EulerPhi[n]+r[n]==2n, Print[n]], {n, 320000000}]
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CROSSREFS
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KEYWORD
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base,more,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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