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A047900 a(1) = 8; for n > 0, a(n+1) = a(n) * sum of digits of a(n). 11

%I

%S 8,64,640,6400,64000,640000,6400000,64000000,640000000,6400000000,

%T 64000000000,640000000000,6400000000000,64000000000000,

%U 640000000000000,6400000000000000,64000000000000000,640000000000000000

%N a(1) = 8; for n > 0, a(n+1) = a(n) * sum of digits of a(n).

%C After the 2nd element, every element has the same beginning.

%C a(3+k) = 10 * a(2+k).

%H Reinhard Zumkeller, <a href="/A047900/b047900.txt">Table of n, a(n) for n = 1..250</a>

%F a(n+1) = A057147(a(n)). - _Reinhard Zumkeller_, Mar 19 2014

%p P:=proc(n) local a,i,k,w; a:=8; print(a); for i from 1 by 1 to n do w:=0;k:=a; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; a:=a*w; print(a); od; end: P(1000); # _Paolo P. Lava_, Apr 27 2007

%t NestList[# Total[IntegerDigits[#]]&,8,20] (* or *) Join[{8},NestList[ 10#&,64,20]] (* _Harvey P. Dale_, Jul 03 2020 *)

%o (Haskell)

%o a047900 n = a047900_list !! (n-1)

%o a047900_list = iterate a057147 8 -- _Reinhard Zumkeller_, Mar 19 2014

%Y Cf. A047892 (start=2), A047912 (start=3), A047897 (start=5), A047898 (start=6), A047899 (start=7), A047901 (start=9), A047902 (start=11).

%K easy,nonn,base

%O 1,1

%A Miklos SZABO (mike(AT)ludens.elte.hu)

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Last modified August 3 22:03 EDT 2021. Contains 346441 sequences. (Running on oeis4.)