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 A104561 #3 Mar 30 2012 18:36:45
%S A104561 1,-1,1,-2,6,-30,204,-1944,23340,-360060,6692280,-151908120,
%T A104561 4032593040,-126425330640,4537069829880,-187762669281600,
%U A104561 8751745668796200,-462088269954518760,27132285729049971120,-1779812144439507990000,128512316060872730854560
%N A104561 Column 0 of triangle A104560.
%C A104561 A104560 equals the matrix inverse of A104559, where A104559(n,k) = C(n-[k/2],[(k+1)/2])*C(n-[(k+1)/2],[k/2]).
%o A104561 (PARI) {a(n)=local(M);M=matrix(n+1,n+1,m,j,if(m>=j, binomial(m-1-(j-1)\2,j\2)*binomial(m-1-j\2,(j-1)\2))); return((M^-1)[n+1,1])}
%Y A104561 Cf. A104559, A104560.
%K A104561 sign
%O A104561 0,4
%A A104561 _Paul D. Hanna_, Mar 16 2005