A109318 - OEIS

%I #5 Mar 30 2012 18:36:49

%S 1,2,8,36,176,920,5080,29336,175752,1085496,6877240,44518520,

%T 293513784,1965904984,13348449784,91723622936,636923476728,

%U 4463989946072,31545992160568,224580029779608,1609455072125816,11603437881340888

%N Column 2 of triangle T=A109316 where T(n,k) = [T^2](n-1,k) + [T^2](n-2,k-1) and T^2 is the matrix square of A109316.

%o (PARI) {a(n)=local(A=Mat(1),B);for(m=1,n+3,B=matrix(m,m); for(i=1,m, for(j=1,i,if(j==i,B[i,j]=1,if(i==2,B[i,j]=1, B[i,j]=(A^2)[i-1,j]+if(j>1,(A^2)[i-2,j-1])));));A=B); return(A[n+3,3])}

%Y Cf. A109316 (triangle), A109317 (column 0), A109319 (row sums), A000108.

%K nonn

%O 0,2

%A _Paul D. Hanna_, Jul 07 2005