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 A109155 Column 2 of triangle A109152. 6

%I

%S 1,3,6,24,102,516,2814,16752,106026,712260,5027190,37158600,286141638,

%T 2289018708,18961164774,162271001760,1431533922642,12994777356228,

%U 121174578691398,1159065402957240,11357543381281638,113876839666712676

%N Column 2 of triangle A109152.

%C Triangular matrix T=A109152 satisfies: T(n,k) = [T^2](n-1,k) for n>k+1>=1, with T(n,n) = 1 and T(n+1,n) = n+1 for n>=0.

%o (PARI) {a(n)=local(M=matrix(n+3,n+3));M=M^0;for(i=1,n, M=matrix(n+3,n+3,r,c,if(r>=c,if(r==c,1,if(r==c+1,c,(M^2)[r-1,c]))))); return(M[n+3,3])}

%Y Cf. A109152 (triangle), A109153 (column 0), A109154 (column 1), A109156 (row sums).

%K nonn

%O 0,2

%A _Paul D. Hanna_, Jun 20 2005

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Last modified September 22 07:34 EDT 2020. Contains 337289 sequences. (Running on oeis4.)