A105616 - OEIS

%I #3 Mar 30 2012 18:36:45

%S 1,4,26,226,2426,30826,451586,7489426,138722426,2839238026,

%T 63654973826,1551919194226,40888965122426,1157981114051626,

%U 35083865696279426,1132449247218851026,38800104353355372026,1406432065083818193226

%N Column 1 of triangle A105615.

%C Also equals column 0 of triangle A105623 (offset 1), where A105623 equals the matrix square-root of triangle A105615.

%o (PARI) {a(n)=if(n<0,0,(matrix(n+2,n+2,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+2,2])}

%Y Cf. A105615, A105623.

%K nonn

%O 0,2

%A _Paul D. Hanna_, Apr 16 2005