This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A136538 #11 Aug 13 2019 07:04:35
%S A136538 2,4,8,42,84,2763,4032,8064,67314,86558,291483,2700063,2700000063,
%T A136538 4039603962,46420566582,6739054689866
%N A136538 Numbers n such that reversal(n)=2*phi(n).
%C A136538 If m>1 and p=3*10^m+7 is prime then n=9*p is in the sequence (the proof is easy). If n is an even term of the sequence and the largest digit of n is less than 5(3) then 2n is (both numbers 2n & 4n are) in the sequence (the proof is easy).
%C A136538 a(17) > 10^13. - _Giovanni Resta_, Aug 12 2019
%e A136538 Reversal(42)=24=2*12=2*phi(42), so 42 is in the sequence. [Example corrected Jan 25 2008]
%t A136538 Do[If[FromDigits@Reverse@IntegerDigits@n==2*EulerPhi[n], Print[n]],{n,100000000}]
%Y A136538 Cf. A000010, A004086, A069215, A114930, A114931, A136539.
%K A136538 nonn,base,more
%O A136538 1,1
%A A136538 _Farideh Firoozbakht_, Jan 04 2008
%E A136538 a(13)-a(15) from _Giovanni Resta_, Oct 28 2012
%E A136538 a(16) from _Giovanni Resta_, Aug 12 2019