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%I #14 Aug 13 2019 07:22:35
%S 1,95913,959913,526108071,950039541,95999999913,534629946141,
%T 950947559613,3378374216211,9599999999913
%N Numbers n such that phi(n) is the arithmetic mean of n and reversal(n).
%C A number of the form 3*(32*10^n-29) is in the sequence iff n>1 and 1/3*(32*10^n-29) is prime (the proof is easy). The first three such terms are 3*(32*10^3-29),3*(32*10^4-29)& 3*(32*10^9-29).
%C a(11) > 10^13. - _Giovanni Resta_, Aug 12 2019
%e phi(950039541)=1/2*(950039541+145930059) so 950039541 is in the sequence.
%t r[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Do[c=r[n];If[c+n== 2EulerPhi[n],Print[n]],{n,200000000}]
%Y Cf. A000010, A004086, A130000.
%K nonn,base,more
%O 1,2
%A _Farideh Firoozbakht_, Apr 29 2007
%E a(6)-a(8) from _Giovanni Resta_, Oct 28 2012
%E a(9)-a(10) from _Giovanni Resta_, Aug 12 2019
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