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 A069225 #18 Jun 07 2025 15:51:07 %S A069225 1,65,2771,10920,158804,2413091,16636354,117650080,140766297, %T A069225 630947067,4639526938,153896850898 %N A069225 Numbers k such that phi(k) is the reversal of sigma(k). %C A069225 a(13) > 10^12. - _Giovanni Resta_, Nov 03 2012 %e A069225 phi(65) = 48 = reversal(84) = reversal(sigma(65)), so 65 belongs to the sequence. %e A069225 n=2413091, sigma[n]=2528032, phi[n]=2308152=rev[sigma[n]]. %t A069225 Select[Range[10^6], EulerPhi[ # ] == FromDigits[Reverse[IntegerDigits[DivisorSigma[1, # ]]]] &] %Y A069225 Cf. A000010, A000203, A004086. %K A069225 base,nonn %O A069225 1,2 %A A069225 _Joseph L. Pe_, Apr 12 2002 %E A069225 a(6)-a(8) from _Labos Elemer_, Oct 22 2004 %E A069225 a(9)-a(11) from _Donovan Johnson_, Jan 14 2011 %E A069225 a(12) from _Giovanni Resta_, Nov 03 2012