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 A117296 #9 Apr 21 2020 12:04:06 %S A117296 1,2,3,4,5,6,7,8,9,10,12,14,15,16,18,20,23,24,30,46,67,69,89,92,115, %T A117296 134,138,178,184,223,230,233,263,276,283,289,293,295,301,321,381,387, %U A117296 411,428,441,446,466,472,508,526,535,548,566,578,586,590 %N A117296 Numbers n for which phi(n) is a palindrome. %H A117296 Harvey P. Dale, <a href="/A117296/b117296.txt">Table of n, a(n) for n = 1..2000</a> %e A117296 69 is in the sequence because phi(69)=44 which is a palindrome. %t A117296 Select[Range[600],FromDigits[Reverse[IntegerDigits[EulerPhi[ # ]]]]==EulerPhi[ # ] &] (* _Stefan Steinerberger_, Apr 24 2006 *) %t A117296 Select[Range[600],PalindromeQ[EulerPhi[#]]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Apr 21 2020 *) %Y A117296 Cf. A002113. %K A117296 base,nonn %O A117296 1,2 %A A117296 Luc Stevens (lms022(AT)yahoo.com), Apr 23 2006 %E A117296 Corrected and extended by _Stefan Steinerberger_, Apr 24 2006