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 A105617 #3 Mar 30 2012 18:36:45
%S A105617 1,6,50,522,6498,93666,1532970,28079082,569212578,12655466946,
%T A105617 306280630890,8017054975242,225716319717858,6802519195684386,
%U A105617 218521006115328810,7454198349649868202,269114811307118424738
%N A105617 Column 2 of triangle A105615.
%o A105617 (PARI) {a(n)=if(n<0,0,(matrix(n+3,n+3,m,j,if(m>=j,if(m==j,1,if(m==j+1,-2*j, polcoeff(1/sum(i=0,m-j,(2*i)!/i!/2^i*x^i)+O(x^m),m-j) ))))^-1)[n+3,3])}
%Y A105617 Cf. A105615.
%K A105617 nonn
%O A105617 0,2
%A A105617 _Paul D. Hanna_, Apr 16 2005