A109154 Column 1 of triangle A109152.

1, 2, 4, 14, 56, 262, 1348, 7574, 45616, 292442, 1978788, 14060654, 104403304, 807162070, 6476169012, 53781863598, 461194543136, 4075567775538, 37048022605956, 345883045698222, 3311798037556952, 32480125869403430

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+2, n+2)); M=M^0; for(i=1, n, M=matrix(n+2, n+2, r, c, if(r>=c, if(r==c, 1, if(r==c+1, c, (M^2)[r-1, c]))))); return(M[n+2, 2])}

Crossrefs

Cf. A109152 (triangle), A109153 (column 0), A109155 (column 2), A109156 (row sums).

Sequence in context: A047990 A000939 A367558 * A030853 A306150 A030962

Adjacent sequences: A109151 A109152 A109153 * A109155 A109156 A109157

Keyword

nonn

Author

Paul D. Hanna, Jun 20 2005

Status

approved