A121421 Column 0 of triangle A121420.

1, 3, 12, 76, 711, 9054, 147471, 2938176, 69328365, 1891371807, 58575539361, 2030011517685, 77827890696820, 3270046577551695, 149407542447596319, 7374639622066056408, 391044078030333899385, 22168014954558449549349

Offset: 0

Author

Paul D. Hanna, Aug 23 2006

Keywords

• nonn

Comments

Also column 2 of square array A136733.

A121420 is the matrix cube of triangle A121412; row n of triangle T=A121412 equals row (n-1) of T^(n+1) with an appended '1'.

Crossrefs

Cf. A121420 (triangle); other columns: A121422, A121423.

Cf. A136733; A101483, A121418; A121425.

Programs

PARI

{a(n)=local(A=Mat(1), B); for(m=1, n+1, B=matrix(m, m); for(i=1, m, for(j=1, i, if(j==i, B[i,j]=1, B[i, j]=(A^i)[i-1, j]); )); A=B); return((A^3)[n+1, 1])}

Extensions

Edited by N. J. A. Sloane, Oct 30 2008 at the suggestion of R. J. Mathar