Search: id:A135238
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%I A135238
%S A135238 1,2,8,2991,65034,880374
%N A135238 Numbers n such that phi(sigma(n))=reversal(n).
%C A135238 If both numbers 10^m-3 & 5*10^(m-1)-1 are primes and n=3*(10^m-3) then 
               phi(sigma(n))=reversal(n), namely n is in the sequence (the proof 
               is easy). Conjecture: n=2991 is the only such term of the sequence. 
               there is no further term up to 35*10^7.
%e A135238 phi(sigma(880374))=phi(1920960)=473088=reversal(880374), so 880374 is 
               in the sequence.
%t A135238 reversal[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Do[If[EulerPhi[DivisorSigma[1,
               n]]==reversal[n],Print[n]], {n,350000000}]
%Y A135238 Cf. A071525.
%Y A135238 Sequence in context: A027733 A054874 A057841 this_sequence A133376 A160814 
               A038582
%Y A135238 Adjacent sequences: A135235 A135236 A135237 this_sequence A135239 A135240 
               A135241
%K A135238 base,more,nonn
%O A135238 1,2
%A A135238 Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 26 2007

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