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 A066713 #23 Feb 16 2025 08:32:45
%S A066713 2,4,8,16,77,55,11,499,89,277,2255,145,11,1111,44567,111499,12299,
%T A066713 1234,3467,113467,677789,144556,1222889,14445667,4577789,55669999,
%U A066713 1134899,11356999,12237899,445557799,1223555555,11113366,1122222266
%N A066713 RATS(2^n): Reverse Add the digits of 2^n, Then Sort: a(n) = A036839(2^n).
%C A066713 A114611(a(n)) = 0, as A114611(A000079(n)) = 0. - _Reinhard Zumkeller_, Mar 14 2012
%H A066713 Reinhard Zumkeller, <a href="/A066713/b066713.txt">Table of n, a(n) for n = 0..1000</a>
%H A066713 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/RATSSequence.html">RATS Sequence</a>
%o A066713 (Haskell)
%o A066713 a066713 = a036839 . (2 ^) -- _Reinhard Zumkeller_, Mar 14 2012
%o A066713 (Python)
%o A066713 def A066713(n):
%o A066713 m = 2**n
%o A066713 return int(''.join(sorted(str(m+int(str(m)[::-1]))))) # _Chai Wah Wu_, Feb 07 2020
%Y A066713 See A004000, A036839 for more information.
%K A066713 nonn,base
%O A066713 0,1
%A A066713 _N. J. A. Sloane_, Jan 19 2002