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 A075475 #15 Aug 12 2019 23:13:01 %S A075475 1,3,15,129,270,833,5044,59815,9633693,26427528,4642779313, %T A075475 26594615202,62935243460,91770096041,1648209018135 %N A075475 Numbers n such that reverse(phi(n+1)) = phi(n). %C A075475 a(12) > 25*10^9. - _Donovan Johnson_, Jun 09 2011 %C A075475 a(16) > 2*10^12. - _Giovanni Resta_, Aug 12 2019 %e A075475 n=59815: phi(n) = 40992, phi(n+1) = 29904 = rev(phi(n)). %t A075475 Select[Range[60000], IntegerReverse[EulerPhi[# + 1]] == EulerPhi[#] &] (* _Giovanni Resta_, Aug 12 2019 *) %o A075475 (PARI) isok(n) = eulerphi(n) == fromdigits(Vecrev(digits(eulerphi(n+1)))); \\ _Michel Marcus_, Aug 12 2019 %Y A075475 Cf. A004086, A069225, A074241, A074242. %K A075475 nonn,base,more %O A075475 1,2 %A A075475 _Labos Elemer_, Sep 20 2002 %E A075475 a(9)-a(11) from _Donovan Johnson_, Jun 09 2011 %E A075475 a(12)-a(15) from _Giovanni Resta_, Aug 12 2019