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 A115897 #19 Jul 15 2021 21:23:56 %S A115897 1,2,3,4,10,11,21,49,92,101,115,131,145,186,200,201,206,207,221,226, %T A115897 227,240,272,302,310,313,327,342,344,370,374,388,403,406,409,413,419, %U A115897 425,439,449,880,948,1015,1055,1132,1165,1385,1443,1680,1755,1785 %N A115897 Numbers k such that sigma(k) + phi(k) is a palindrome. %H A115897 Michael De Vlieger, <a href="/A115897/b115897.txt">Table of n, a(n) for n = 1..5000</a> %e A115897 sigma(1055) + phi(1055) = 1272 + 840 = 2112. %t A115897 Select[Range@ 1800, Reverse@ # == # &@ IntegerDigits[DivisorSigma[1, #] + EulerPhi@ #] &] (* _Michael De Vlieger_, Jul 22 2016 *) %t A115897 Select[Range[2000],PalindromeQ[DivisorSigma[1,#]+EulerPhi[#]]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Mar 29 2020 *) %o A115897 (PARI) ispal(n)=n=digits(n); Vecrev(n)==n %o A115897 is(n,f=factor(n))=ispal(sigma(f)+eulerphi(f)) \\ _Charles R Greathouse IV_, Jul 22 2016 %Y A115897 Cf. A115895, A115896. %K A115897 nonn,base %O A115897 1,2 %A A115897 _Giovanni Resta_, Feb 06 2006