A113991 Column 2 of triangle A113988, which is the matrix square of A113983: a(n) = [A113983^2](n+2,2).

1, 6, 26, 108, 468, 2194, 11294, 64152, 402072, 2773606, 20981626, 173331444, 1557019148, 15144482402, 158854971230, 1790084290832, 21593325563600, 277903063486054, 3804108755321242, 55227351469322460, 848094468268734116

Offset

0,2

Links

Table of n, a(n) for n=0..20.

Prog

(PARI) a(n)=local(A, B); A=Mat(1); for(m=2, n+3, B=matrix(m, m); for(i=1, m, for(j=1, i, if(i<3 || j==1 || j==i, B[i, j]=1, B[i, j]=A[i-1, j-1]+(A^2)[i-2, j-1] ); )); A=B); (A^2)[n+3, 3]

Crossrefs

Cf. A113988, A113989 (column 0), A113990 (column 1), A113992 (column 3).

Sequence in context: A027996 A020989 A079675 * A267578 A255467 A145374

Adjacent sequences: A113988 A113989 A113990 * A113992 A113993 A113994

Keyword

nonn

Author

Paul D. Hanna, Nov 12 2005

Status

approved