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 A173292 #10 Aug 22 2017 15:09:17 %S A173292 5,45,405,4005,40010,400005,4000005,40000010,400000015,4000000015, %T A173292 40000000015,400000000015,4000000000010,40000000000015, %U A173292 400000000000020,-1,-1,-1,4000000000000000020,40000000000000000015,-1 %N A173292 a(n)! has exactly 10^n trailing zeros (a(n) = -1 if no such number exists). %H A173292 David S. Hart, James E. Marengo, Darren A. Narayan, and David S. Ross, <a href="http://www.ingentaconnect.com/content/maa/cmj/2008/00000039/00000002/art00009"> On the number of trailing zeros in n!</a>, College Math. J., 39(2) (2008) p 139-145. %H A173292 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]. %H A173292 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 %Y A173292 Cf. A173558 (at least 10^n trailing zeros). %K A173292 base,sign %O A173292 0,1 %A A173292 _José María Grau Ribas_, Feb 15 2010, Feb 22 2010