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%I #6 Jun 13 2017 22:13:23
%S 1,4,20,140,1460,23884,639156,28895052,2260707508,311748794188,
%T 76846781851828,34240231941576524,27825184844063467700,
%U 41547951604100714698572,114705005843089453002549428
%N Column 2 of triangle A098539, which shifts left one column under the matrix square.
%o (PARI) a(n)=local(A,B,C,m);A=matrix(1,1);A[1,1]=1; for(m=2,n+3,B=A^2;C=matrix(m,m);for(j=1,m, for(k=1,j, if(j<3 || k==j || k>m-1,C[j,k]=1,if(k==1,C[j,k]=B[j-1,1],C[j,k]=B[j-1,k-1])); ));A=C);A[n+3,3]
%Y Cf. A098539, A098540.
%K nonn
%O 0,2
%A _Paul D. Hanna_, Sep 13 2004
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