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 A117259 #4 Mar 30 2012 18:36:56
%S A117259 1,1,-2,32,-2560,917504,-1409286144,9070970929152,-241505530017742848,
%T A117259 26378844025404658810880,-11755594669932654094842855424,
%U A117259 21291459481433341027538627037495296,-156279993920424129009046403691280672489472
%N A117259 Column 0 of triangle A117258.
%F A117259 a(n) = [prod_{j=0..n-1} (1-2*j)]/n! * 4^(n*(n-1)/2).
%o A117259 (PARI) {a(n)=local(m=1,p=2,q=4,r=1);prod(j=0,n-1,m*r-p*j)/n!*q^(n*(n-1)/2)}
%K A117259 sign
%O A117259 0,3
%A A117259 _Paul D. Hanna_, Mar 14 2006