A047897 a(1) = 5; for n > 0, a(n+1) = a(n) * sum of digits of a(n).

5, 25, 175, 2275, 36400, 473200, 7571200, 166566400, 5663257600, 226530304000, 5663257600000, 226530304000000, 5663257600000000, 226530304000000000, 5663257600000000000, 226530304000000000000, 5663257600000000000000

Offset: 1

Author

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

Keywords

• easy
• nonn
• base

Comments

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

Links

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

Crossrefs

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

Programs

Haskell

a047897 n = a047897_list !! (n-1)
a047897_list = iterate a057147 5  -- Reinhard Zumkeller, Mar 19 2014

Mathematica

NestList[#*Total[IntegerDigits[#]]&,5,20] (* Harvey P. Dale, Jan 25 2014 *)

Formula

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