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 A119837 #9 Nov 21 2013 12:48:58
%S A119837 1,0,-12,-240,-5040,-120960,-3326400,-103783680,-3632428800,
%T A119837 -141145804800,-6033983155200,-281585880576000,-14248245557145600,
%U A119837 -777177030389760000,-45464856277800960000,-2839804869044183040000,-188644180586506444800000
%N A119837 a(n)=(2n)!/n!-(2n)!/(n-1)!.
%C A119837 Row sums of number triangle A119836.
%F A119837 a(n)=A001813(n)-2*A001814(n).
%t A119837 f[n_]:=Module[{n2f=(2n)!},n2f/n!-n2f/(n-1)!]; f/@Range[0,20] (* _Harvey P. Dale_, Feb 13 2011 *)
%K A119837 easy,sign
%O A119837 0,3
%A A119837 _Paul Barry_, May 25 2006