A230028 - OEIS

%I #8 Dec 18 2013 11:06:27

%S 104,824,800024,8000024,84803024,8483021444

%N Numbers n such that phi(n) = reversal(n-20).

%C If p=10^m+3 is prime then 8*p is in the sequence.

%C 84803024 is the only known term of the sequence which is not of this form.

%C a(7) > 10^11. - _Giovanni Resta_, Dec 13 2013

%e phi(104)=48=reversal(84)=reversal(104-20).

%t Do[If[EulerPhi[n]==FromDigits[Reverse[IntegerDigits[n-20]]],Print[n]],{n,21,90000000}]

%Y Cf. A000010, A004086.

%K nonn,base,bref,more

%O 1,1

%A _Farideh Firoozbakht_, Dec 13 2013

%E a(6) from _Giovanni Resta_, Dec 13 2013