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 A047900 #17 Feb 19 2024 01:54:41
%S A047900 8,64,640,6400,64000,640000,6400000,64000000,640000000,6400000000,
%T A047900 64000000000,640000000000,6400000000000,64000000000000,
%U A047900 640000000000000,6400000000000000,64000000000000000,640000000000000000
%N A047900 a(1) = 8; for n > 0, a(n+1) = a(n) * sum of digits of a(n).
%C A047900 After the 2nd element, every element has the same beginning.
%C A047900 a(3+k) = 10 * a(2+k).
%H A047900 Reinhard Zumkeller, <a href="/A047900/b047900.txt">Table of n, a(n) for n = 1..250</a>
%F A047900 a(n+1) = A057147(a(n)). - _Reinhard Zumkeller_, Mar 19 2014
%t A047900 NestList[# Total[IntegerDigits[#]]&,8,20] (* or *) Join[{8},NestList[ 10#&,64,20]] (* _Harvey P. Dale_, Jul 03 2020 *)
%o A047900 (Haskell)
%o A047900 a047900 n = a047900_list !! (n-1)
%o A047900 a047900_list = iterate a057147 8 -- _Reinhard Zumkeller_, Mar 19 2014
%Y A047900 Cf. A047892 (start=2), A047912 (start=3), A047897 (start=5), A047898 (start=6), A047899 (start=7), A047901 (start=9), A047902 (start=11).
%K A047900 easy,nonn,base
%O A047900 1,1
%A A047900 Miklos SZABO (mike(AT)ludens.elte.hu)