A113990 Column 1 of triangle A113988, which is the matrix square of A113983: a(n) = [A113983^2](n+1,1).

1, 4, 12, 36, 116, 416, 1680, 7656, 39256, 225348, 1439868, 10179116, 79153484, 673262240, 6231517920, 62461031920, 675005395152, 7832909636740, 97238472215564, 1286967352638292, 18102901048062404, 269852768731391808

Offset

0,2

Links

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

Prog

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

Crossrefs

Cf. A113988, A113989 (column 0), A113991 (column 2), A113992 (column 3).

Sequence in context: A000781 A192205 A055395 * A231179 A331717 A192010

Adjacent sequences: A113987 A113988 A113989 * A113991 A113992 A113993

Keyword

nonn

Author

Paul D. Hanna, Nov 12 2005

Status

approved