OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Multiplicative Persistence
EXAMPLE
239 -> [ 54 ][ 20 ][ 0 ] -> one digit in three steps.
MAPLE
mp:= proc(n) option remember;
if n <= 9 then return 0 fi;
1+procname(convert(convert(n, base, 10), `*`))
end proc:
select(mp=3, [$1..1000]); # Robert Israel, Feb 12 2019
MATHEMATICA
mp3Q[n_]:=Length[NestWhileList[Times@@IntegerDigits[#]&, n, #>9&]]==4; Select[Range[300], mp3Q] (* Harvey P. Dale, May 23 2015 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Sep 15 1998
EXTENSIONS
Offset corrected by Robert Israel, Feb 12 2019
STATUS
approved