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 A072395 #19 Aug 06 2019 10:09:01 %S A072395 1,21,63,291,2991,6102,46676013,69460293,2346534651,6313047393, %T A072395 23400000651,80050617822,234065340651,234659934651,2340000000651, %U A072395 2934000006591 %N A072395 Numbers n such that reverse(phi(n)) = n. %C A072395 For all n, a(n) = reversal(A085331(n)), so see Comment on A085331. This sequence is a subsequence of A069215 and if m is a term of A069215 and 10 doesn't divide m then m is in this sequence. - _Farideh Firoozbakht_, Jan 09 2005 %C A072395 a(13) > 10^11. - _Donovan Johnson_, Feb 03 2012 %C A072395 a(17) > 10^13. - _Giovanni Resta_, Aug 06 2019 %e A072395 reverse(phi(6102)) = reverse(2016) = 6102, so 6102 is a term of the sequence. %t A072395 Select[Range[10^5], FromDigits[Reverse[IntegerDigits[EulerPhi[#]]]] == # &] (* corrected by _Harvey P. Dale_, Oct 03 2011 *) %Y A072395 Cf. A085331, A069215, A102278. %K A072395 nonn,base,more %O A072395 1,2 %A A072395 _Joseph L. Pe_, Jul 21 2002 %E A072395 More terms from _Robert G. Wilson v_, Jul 23 2002 %E A072395 More terms from _Farideh Firoozbakht_, Jan 09 2005 %E A072395 a(10)-a(12) from _Donovan Johnson_, Feb 03 2012 %E A072395 a(13)-a(16) from _Giovanni Resta_, Aug 06 2019