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 A033648 #30 Jul 08 2025 19:54:12
%S A033648 3,6,12,33,66,132,363,726,1353,4884,9768,18447,92928,175857,934428,
%T A033648 1758867,9447438,17794887,96644658,182289327,906271608,1712444217,
%U A033648 8836886388,17673772776,85401510447,159803020905,668823329856,1327746658722,3606313135953,7201626272016
%N A033648 Trajectory of 3 under map x->x + (x-with-digits-reversed).
%C A033648 Normally one stops as soon as a palindrome is reached.
%C A033648 A Reverse and Add! sequence.
%H A033648 Alois P. Heinz, <a href="/A033648/b033648.txt">Table of n, a(n) for n = 0..1000</a> (first 251 terms from Reinhard Zumkeller)
%H A033648 <a href="/index/Res#RAA">Index entries for sequences related to Reverse and Add!</a>
%p A033648 a:= proc(n) option remember; `if`(n=0, 3, (h-> h+ (s->
%p A033648 parse(cat(s[-i]$i=1..length(s))))(""||h))(a(n-1)))
%p A033648 end:
%p A033648 seq(a(n), n=0..40); # _Alois P. Heinz_, Jun 18 2014
%t A033648 NestList[ # + FromDigits@Reverse@IntegerDigits@# &, 3, 29] (* _Robert G. Wilson v_, Dec 16 2005 *)
%o A033648 (Haskell)
%o A033648 a033648 n = a033648_list !! n
%o A033648 a033648_list = iterate a056964 3 -- _Reinhard Zumkeller_, Sep 22 2011
%Y A033648 Cf. A006960, A001127, A033649, A033650, A033651.
%Y A033648 Cf. A056964, A004086.
%Y A033648 Row n=3 of A243238.
%K A033648 nonn,base
%O A033648 0,1
%A A033648 _N. J. A. Sloane_