OFFSET
1,3
COMMENTS
Equivalently, possible values of 10-adic valuation of n!. - Joerg Arndt, Sep 21 2020
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
a(n) ~ 5*n/4. - Vaclav Kotesovec, Sep 21 2020
G.f.: 1/(1-x) * Sum_{k>=0} x^(5^k)/(1-x^5^k). - Joerg Arndt, Sep 21 2020
MATHEMATICA
zOF[n_Integer?Positive]:=Module[{maxpow=0}, While[5^maxpow<=n, maxpow++]; Plus@@Table[ Quotient[n, 5^i], {i, maxpow-1}]]; Attributes[zOF]={Listable}; zOF[Range[1000]]//Union (* Harvey P. Dale, Dec 06 2023 *)
PROG
(Haskell)
a191610 1 = 0
a191610 n = sum $ takeWhile (> 0) $ map ((n - 1) `div`) a000351_list
-- Reinhard Zumkeller, Oct 31 2012
(Python)
# requires Python 3.2 and higher
from itertools import accumulate
from sympy import multiplicity
A191610 = [0]+list(accumulate(multiplicity(5, n) for n in range(5, 10**3, 5)))
# Chai Wah Wu, Sep 05 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
José María Grau Ribas, Jun 09 2011
STATUS
approved