A109155 Column 2 of triangle A109152.

1, 3, 6, 24, 102, 516, 2814, 16752, 106026, 712260, 5027190, 37158600, 286141638, 2289018708, 18961164774, 162271001760, 1431533922642, 12994777356228, 121174578691398, 1159065402957240, 11357543381281638, 113876839666712676

Offset

0,2

Comments

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.

Links

Table of n, a(n) for n=0..21.

Prog

(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])}

Crossrefs

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

Sequence in context: A152761 A295761 A262349 * A338112 A294381 A081072

Adjacent sequences: A109152 A109153 A109154 * A109156 A109157 A109158

Keyword

nonn

Author

Paul D. Hanna, Jun 20 2005

Status

approved