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 A074241 #9 Aug 12 2019 23:13:41 %S A074241 1,3,15,129,833,5044,59815,267335,297863,9633693,4642779313, %T A074241 62935243460,91770096041,1648209018135 %N A074241 Numbers n such that phi(n+1) = reverse(phi(n)). %C A074241 a(15) > 2*10^12. - _Giovanni Resta_, Aug 12 2019 %e A074241 phi(129 + 1) = 48 = reverse(84) = reverse(phi(129)), so 129 is a term of the sequence. %t A074241 Select[Range[10^5], FromDigits[Reverse[IntegerDigits[EulerPhi[ # ]]]] == EulerPhi[ # + 1] &] %o A074241 (PARI) isok(n) = eulerphi(n+1) == fromdigits(Vecrev(digits(eulerphi(n)))); \\ _Michel Marcus_, Aug 12 2019 %Y A074241 Cf. A004086, A075475. %K A074241 nonn,base,more %O A074241 1,2 %A A074241 _Joseph L. Pe_, Sep 18 2002 %E A074241 a(8)-a(14) from _Giovanni Resta_, Aug 12 2019