A105627 - OEIS

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

%S 1,6,48,480,5736,79584,1256808,22262640,437315016,9438589824,

%T 222109617288,5661445534800,155427839133096,4573268363775264,

%U 143592923776842408,4792636497324986160,169456698405536983176

%N Column 1 of triangle A105626.

%C A105626 equals the cube of the matrix square-root of triangle A105615.

%o (PARI) {a(n)=local(R,M=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)))))^-3); R=(M+M^0)/2;for(i=1,floor(2*log(n+2)),R=(R+M*R^(-1))/2); return(if(n<0,0,R[n+2,2]))}

%Y Cf. A105615, A105626.

%K nonn

%O 0,2

%A _Paul D. Hanna_, Apr 16 2005