A047897 - OEIS

%I #19 Feb 17 2024 10:34:23

%S 5,25,175,2275,36400,473200,7571200,166566400,5663257600,226530304000,

%T 5663257600000,226530304000000,5663257600000000,226530304000000000,

%U 5663257600000000000,226530304000000000000,5663257600000000000000

%N a(1) = 5; for n > 0, a(n+1) = a(n) * sum of digits of a(n).

%C After a(9), every second element has the same beginning. a(11+2k) = 40 * a(10+2k) = 40 * 25 * a(9+2k).

%H Reinhard Zumkeller, <a href="/A047897/b047897.txt">Table of n, a(n) for n = 1..250</a>

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

%t NestList[#*Total[IntegerDigits[#]]&,5,20] (* _Harvey P. Dale_, Jan 25 2014 *)

%o (Haskell)

%o a047897 n = a047897_list !! (n-1)

%o a047897_list = iterate a057147 5  -- _Reinhard Zumkeller_, Mar 19 2014

%Y Cf. A047892 (start=2), A047912 (start=3), A047898 (start=6), A047899 (start=7), A047900 (start=8), A047901 (start=9), A047902 (start=11).

%K easy,nonn,base

%O 1,1

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