This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
f[n_] := IntegerExponent[Prime@n!, 10]; Complement[ Range[0, 157], Array[f, 115]] (* Robert G. Wilson v, Nov 05 2010 *) zOF[n_Integer?Positive]:=Module[{maxpow=0},While[5^maxpow<=n,maxpow++];Plus@@Table[ Quotient[n,5^i],{i,maxpow-1}]]; Attributes[zOF]={Listable}; With[{z=Union[zOF[Prime[Range[ 150]]]]},Complement[ Range[Max[z]],z]] (* Harvey P. Dale, Sep 17 2024 *)
a(0) = 0 as 0! = 1 does not contain '0'. a(1) = 5 as 5! = 120 contains '0'. a(2) = 10 as 10! = 3628800 contains '00' and 10 is the smallest integer for which the condition is met.
\\ uses is() from A000966 f(k, special, sz, sz1) = my(f=k!); if (special, s=Str(f/10^valuation(f, 10)), s=Str(k!)); #strsplit(s, sz) - #strsplit(s, sz1); a(n) = if (n==0, return(0)); my(sz= concat(vector(n, k, "0")), sz1=concat(sz, "0"), k=1,special=is(n)); while (f(k, special, sz, sz1) != 1, k++); k; \\ Michel Marcus, Oct 25 2023
# Python version 2.7
from math import factorial as fct
def trailing_zero(n):
k=0
while n!=0:
n/=5
k+=n
return k
def A255400():
index = 1
f = 1
while True:
if trailing_zero(f) == index:
print("A255400("+str(index)+") = " +str(f))
index += 1
elif trailing_zero(f) > index:
while True:
clnzer = str(fct(f))[:-trailing_zero(f)]
if index*'0' in clnzer and (index+1)*'0' not in clnzer:
print("A255400("+str(index)+") = " +str(f))
index += 1
f = 0
break
f +=1
f +=1
return
import re def A255400(n): f, i, s = 1, 0, re.compile('[0-9]*[1-9]0{'+str(n)+'}[1-9][0-9]*') while s.match(str(f)+'1') is None: i += 1 f *= i return i # Chai Wah Wu, Apr 02 2015
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