A113989 Column 0 of triangle A113988, which is the matrix square of A113983: a(n) = [A113983^2](n,0).

1, 2, 4, 8, 18, 46, 136, 464, 1818, 8122, 41076, 233472, 1480946, 10412590, 80634432, 683674832, 6312152354, 63144706754, 681317547508, 7896054343496, 97919789763074, 1294863406981790, 18200820837825480, 271147632138373600

Offset

0,2

Links

Table of n, a(n) for n=0..23.

Formula

a(n) = A113984(n+1) - 1. a(n) = a(n-2) + A113990(n-2) + 2 for n>=2.

Prog

(PARI) a(n)=local(A, B); A=Mat(1); for(m=2, n+1, 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+1, 1]

Crossrefs

Cf. A113988, A113990 (column 1), A113991 (column 2), A113992 (column 3); A113984, A113983, A113993.

Sequence in context: A308030 A252653 A006771 * A126757 A369386 A034766

Adjacent sequences: A113986 A113987 A113988 * A113990 A113991 A113992

Keyword

nonn

Author

Paul D. Hanna, Nov 12 2005

Status

approved