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%I #4 Jun 14 2017 00:39:18
%S 1,6,51,636,11406,284541,9580386,424183235,24153149813,1735098195632,
%T 154672986360369,16865030992205590,2221033362344695926,
%U 349359800218878205297,64988052594622640286645
%N Column 2 of triangle T=A134523, also equals column 0 of the matrix power T^6, where column k of T = column 0 of matrix power T^{(k+1)(k+2)/2} for k>=0.
%o (PARI) a(n)=local(A, B); A=matrix(1, 1); A[1, 1]=1; for(m=2, n+3, B=matrix(m, m); for(i=1, m, for(j=1, i, if(i<3 || j==i || j>m-1, B[i, j]=1, if(j==1, B[i, 1]=1, B[i, j]=(A^(j*(j+1)/2))[i-j+1, 1])); )); A=B); A[n+3, 3]
%Y Cf. A134523 (triangle); other columns: A134524, A134526.
%K nonn
%O 0,2
%A _Paul D. Hanna_, Nov 15 2007