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A114930
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Numbers n such that phi(n)=2*reversal(n).
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1
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OFFSET
| 1,1
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COMMENTS
| 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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EXAMPLE
| 637062480 is in the sequence because phi(637062480)=2*84260736=
2*reversal(637062480).
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MATHEMATICA
| Do[If[EulerPhi[n]==2*FromDigits[Reverse[IntegerDigits[n]]], Print[n]], {n, 110000000}]
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CROSSREFS
| Cf. A069215, A114931.
Sequence in context: A033288 A057880 A151967 * A068757 A186602 A031836
Adjacent sequences: A114927 A114928 A114929 * A114931 A114932 A114933
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KEYWORD
| base,more,nonn
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AUTHOR
| Farideh Firoozbakht (mymontain(AT)yahoo.com), Jan 29 2006
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