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 A015977 #18 May 11 2022 13:30:54
%S A015977 5,6,7,8,9,19,28,37,39,46,48,49,55,57,58,64,66,67,73,75,76,82,84,85,
%T A015977 91,93,94,109,119,129,139,149,150,151,152,153,154,159,160,161,162,163,
%U A015977 169,170,171,172,173,179,189,208,218,219,228,229,238,239,248
%N A015977 Two iterations of Reverse and Add are needed to reach a palindrome.
%C A015977 The number of iterations starts at 1, so palindromes (cf. A002113) are not excluded. The corresponding sequence excluding palindromes is A065207.
%H A015977 Harvey P. Dale, <a href="/A015977/b015977.txt">Table of n, a(n) for n = 0..1000</a>
%H A015977 <a href="/index/Res#RAA">Index entries for sequences related to Reverse and Add!</a>
%t A015977 Select[Range[250],Boole[PalindromeQ/@Rest[NestList[#+IntegerReverse[#]&,#,2]]] == {0,1}&] (* _Harvey P. Dale_, May 11 2022 *)
%o A015977 (Python)
%o A015977 def ra(n): s = str(n); return int(s) + int(s[::-1])
%o A015977 def ispal(n): s = str(n); return s == s[::-1]
%o A015977 def aupto(limit):
%o A015977 alst = []
%o A015977 for k in range(limit+1):
%o A015977 k2 = ra(k)
%o A015977 if ispal(k2): continue
%o A015977 if ispal(ra(k2)): alst.append(k)
%o A015977 return alst
%o A015977 print(aupto(250)) # _Michael S. Branicky_, May 06 2021
%Y A015977 Cf. A002113, A065207.
%K A015977 nonn,base
%O A015977 0,1
%A A015977 _Robert G. Wilson v_