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.
%I A173228 #39 Feb 23 2018 08:48:17
%S A173228 2,24,249,2499,24999,249998,2499999,24999999,249999998,2499999997,
%T A173228 24999999997,249999999997,2499999999997,24999999999998,
%U A173228 249999999999997,2499999999999996,24999999999999995,249999999999999995,2499999999999999995,24999999999999999996
%N A173228 The number of trailing zeros in (10^n)!
%C A173228 For n > 1, the number a(n) of trailing end 0's in (10^n)! is short of (10^n)/4 by A055223(n). - _Lekraj Beedassy_, Oct 27 2010
%H A173228 Robert G. Wilson v, <a href="/A173228/b173228.txt">Table of n, a(n) for n = 1..100</a>
%H A173228 David S. Hart, James E. Marengo, Darren A. Narayan, and David S. Ross, <a href="http://www.jstor.org/stable/27646601">On the number of trailing zeros in n!</a>, College Math. J., 39(2) (2008) 139-145.
%H A173228 A. M. Oller-Marcen, <a href="http://arxiv.org/abs/0906.4868">A new look at the trailing zeros of n!</a>, arXiv:0906.4868 [math.NT], 2009.
%H A173228 A. M. Oller-Marcen, J. Maria Grau, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL14/Oller/oller3.html">On the Base-b Expansion of the Number of Trailing Zeros of b^k!</a>, J. Int. Seq. 14 (2011) 11.6.8
%F A173228 a(n) = Sum_{k>=1} floor(10^n/5^k). - _Stephen G Cappella_, Dec 13 2017
%t A173228 a[n_] := Sum[Floor[10^n/5^i], {i, Floor[Log[5, 10^n]]}]; Array[f, 18] (* edited by _Robert G. Wilson v_, Jul 22 2012 *)
%o A173228 (Python)
%o A173228 from math import log, ceil
%o A173228 def a(n):
%o A173228 return sum(10**n // 5**k for k in range(1, ceil(log(10, 5) * n)))
%o A173228 # _Stephen G Cappella_, Dec 13 2017
%K A173228 nonn,base
%O A173228 1,1
%A A173228 _José María Grau Ribas_, Feb 13 2010