A047901 a(1) = 9; a(n+1) = a(n) * sum of decimal digits of a(n).

9, 81, 729, 13122, 118098, 3188646, 114791256, 4132485216, 148769467776, 10711401679872, 578415690713088, 41645929731342336, 2998506940656648192, 296852187125008171008, 24045027157125661851648, 2164052444141309566648320

Offset: 1

Author

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

Keywords

• easy
• nonn
• base

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), A047900 (start=8), A047902 (start=11).

Programs

Haskell

a047901 n = a047901_list !! (n-1)
a047901_list = iterate a057147 9  -- Reinhard Zumkeller, Mar 19 2014

Mathematica

NestList[# Total[IntegerDigits[#]]&,9,20] (* Harvey P. Dale, Feb 07 2022 *)

Python

A047901_list, l = [9], 9
for _ in range(10**2):
    l *= sum(int(d) for d in str(l))
    A047901_list.append(l) # Chai Wah Wu, Jan 04 2015

Formula

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

Extensions

Edited by Charles R Greathouse IV, Aug 02 2010