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 A028986 #26 Aug 11 2024 14:41:29
%S A028986 1,2,3,4,5,7,333,17571,1757571,1787871,2249422,4369634,5136315,
%T A028986 412727214,439838934,518686815,541626145,17575757571,52554845525,
%U A028986 4166253526614,5136813186315,5136868686315,5806270726085,7359770779537,172757272757271,513636363636315
%N A028986 Palindromes whose sum of divisors is palindromic.
%C A028986 a(39) >= 10^18. - _Hiroaki Yamanouchi_, Sep 27 2014
%C A028986 Intersection of A002113 and of A028980. - _Michel Marcus_, Apr 06 2015
%H A028986 Hiroaki Yamanouchi, <a href="/A028986/b028986.txt">Table of n, a(n) for n = 1..38</a>
%H A028986 P. De Geest, <a href="https://www.worldofnumbers.com/index.html">World!Of Numbers</a>
%t A028986 palQ[n_]:=Reverse[x=IntegerDigits[n]]==x; t={}; Do[If[palQ[n] && palQ[DivisorSigma[1,n]],AppendTo[t,n]],{n,5.2*10^6}]; t (* _Jayanta Basu_, May 17 2013 *)
%t A028986 Select[Range[52*10^6], AllTrue[{#, DivisorSigma[1, #]}, PalindromeQ] &] (* This naive program is not suitable for generating more than 13 terms of the sequence. *) (* _Harvey P. Dale_, Sep 21 2023 *)
%o A028986 (PARI) a(n)=my(d,i,r);r=vector(#digits(n-10^(#digits(n\11)))+#digits(n\11));n=n-10^(#digits(n\11));d=digits(n);for(i=1,#d,r[i]=d[i];r[#r+1-i]=d[i]);sum(i=1,#r,10^(#r-i)*r[i]) \\ _David A. Corneth_ in A002113, Jun 06 2014
%o A028986 pal(n)=d=digits(n);Vecrev(d)==d
%o A028986 for(n=2,10^5,if(pal(sigma(a(n))),print1(a(n),", "))) \\ _Derek Orr_, Apr 05 2015
%Y A028986 Cf. A002113 (palindromes), A028980 (sigma(n) is a palindrome).
%K A028986 nonn,base
%O A028986 1,2
%A A028986 _Patrick De Geest_
%E A028986 a(18)-a(24) from _Donovan Johnson_, Apr 19 2010
%E A028986 a(25)-a(26) from _Donovan Johnson_, Jun 16 2011