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

1,1

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

Formula

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

Maple

P:=proc(n) local a, i, k, w; a:=5; 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

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A258369 A137383 A049035 * A204461 A121144 A096684

Adjacent sequences: A047894 A047895 A047896 * A047898 A047899 A047900

Keyword

easy,nonn,base

Author

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

Status

approved