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 A166680 #19 May 23 2016 02:47:41
%S A166680 1,-3,-14,-54,-232,-1180,-7104,-49756,-398080,-3582756,-35827600,
%T A166680 -394103644,-4729243776,-61480169140,-860722368016,-12910835520300,
%U A166680 -206573368324864,-3511747261522756,-63211450707409680
%N A166680 a(n) = n*(a(n-1)-4), a(0) = 1.
%H A166680 Vincenzo Librandi, <a href="/A166680/b166680.txt">Table of n, a(n) for n = 0..200</a>
%F A166680 a(n) = n! - 4*floor(e*n!) + 4, n>0. - _Gary Detlefs_, Jun 19 2010
%t A166680 RecurrenceTable[{a[0]==1,a[n]==n(a[n-1]-4)},a,{n,20}] (* _Harvey P. Dale_, Apr 18 2014 *)
%t A166680 FoldList[#1*#2 - 4 #2 &, 1, Range[50]] (* _G. C. Greubel_, May 23 2016 *)
%Y A166680 Cf. A000142, A166554, A165793, A165814.
%K A166680 easy,sign
%O A166680 0,2
%A A166680 _Philippe Deléham_, Oct 18 2009