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 A015980 #11 May 28 2018 11:13:07
%S A015980 69,78,87,96,174,175,181,183,191,192,195,273,274,280,282,290,291,294,
%T A015980 372,373,381,390,393,471,472,480,492,539,570,571,579,591,599,629,638,
%U A015980 649,670,678,679,690,698,699,728,729,737,748,749,769,777
%N A015980 Four iterations of Reverse and Add are needed to reach a palindrome.
%C A015980 The number of iterations starts at 1, so palindromes (cf. A002113) are not excluded. The corresponding sequence excluding palindromes is A065209.
%H A015980 Harvey P. Dale, <a href="/A015980/b015980.txt">Table of n, a(n) for n = 0..1000</a>
%H A015980 <a href="/index/Res#RAA">Index entries for sequences related to Reverse and Add!</a>
%t A015980 ra4Q[n_]:=With[{c=Rest[NestList[#+IntegerReverse[#]&,n,4]]}, PalindromeQ[ Last[c]] && NoneTrue[Most[c],PalindromeQ]]; Select[Range[800],ra4Q] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 28 2018 *)
%Y A015980 A002113, A065209.
%K A015980 nonn,base
%O A015980 0,1
%A A015980 _Robert G. Wilson v_