OFFSET
1,1
LINKS
Daniel Mondot, Table of n, a(n) for n = 1..10000 (terms 1..3000 from Vincenzo Librandi)
Eric Weisstein's World of Mathematics, Multiplicative Persistence
EXAMPLE
129 -> [ 18 ] -> [ 8 ] = one digit in two steps.
MATHEMATICA
mpQ[n_]:=Length[NestWhileList[Times@@IntegerDigits[#]&, n, #>9&]]==3; Select[Range[200], mpQ] (* Harvey P. Dale, Apr 12 2014 *)
PROG
(Python)
from math import prod
def pd(n): return prod(map(int, str(n)))
def ok(n): return n > 9 and (p := pd(n)) > 9 and pd(p) < 10
print([k for k in range(173) if ok(k)]) # Michael S. Branicky, Jan 16 2022
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Sep 15 1998
STATUS
approved