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 A181581 #12 Oct 06 2014 04:14:13 %S A181581 1,9,81,801,8002,80001,800001,8000002,80000003,800000003,8000000003, %T A181581 80000000003,800000000002,8000000000003,80000000000004,0,0,0, %U A181581 800000000000000004,8000000000000000003,0,800000000000000000005,8000000000000000000006,0 %N A181581 Smallest k such that each of the five factorials (5k)!, (5k+1)!, (5k+2)!, (5k+3)! and (5k+4)! has exactly 10^n trailing 0's. Zero, if no such k exists. %C A181581 a(n) = A173558(n)/5 or 0. %H A181581 Hiroaki Yamanouchi, <a href="/A181581/b181581.txt">Table of n, a(n) for n = 0..100</a> %H A181581 <a href="/index/Fa#factorial">Index to sequences related to factorial numbers</a>. %Y A181581 Cf. A027868, A173558. %K A181581 nonn %O A181581 0,2 %A A181581 _Lekraj Beedassy_, Nov 02 2010 %E A181581 a(15)-a(17) corrected and a(18)-a(23) added by _Hiroaki Yamanouchi_, Oct 06 2014