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 A105631 #3 Mar 30 2012 18:36:45
%S A105631 0,1,5,27,195,1833,21125,286451,4453859,78031153,1520668645,
%T A105631 32631020011,764640901539,19431070911513,532315915981605,
%U A105631 15640217893829891,490640673319698179,16368499360721508833,578693283962999831365
%N A105631 Row sums of triangle A105629, which is the matrix logarithm of triangle A105623.
%C A105631 A105623 equals the matrix square-root of triangle A105615.
%o A105631 (PARI) {a(n)=local(L,M=matrix(n+1,n+1,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); L=sum(i=1,#M,(-1)^(i-1)*(M-M^0)^i/i); return(if(n<0,0,sum(k=0,n,L[n+1,k+1])/2))}
%Y A105631 Cf. A105629, A105623, A105615.
%K A105631 nonn
%O A105631 0,3
%A A105631 _Paul D. Hanna_, Apr 16 2005