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

8, 64, 640, 6400, 64000, 640000, 6400000, 64000000, 640000000, 6400000000, 64000000000, 640000000000, 6400000000000, 64000000000000, 640000000000000, 6400000000000000, 64000000000000000, 640000000000000000

Offset: 1

Author

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

Keywords

• easy
• nonn
• base

Comments

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

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

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..250

Crossrefs

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

Programs

Haskell

a047900 n = a047900_list !! (n-1)
a047900_list = iterate a057147 8  -- Reinhard Zumkeller, Mar 19 2014

Mathematica

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

Formula

a(n+1) = A057147(a(n)). - Reinhard Zumkeller, Mar 19 2014