A121422 Column 1 of triangle A121420.

1, 3, 15, 118, 1317, 19311, 352636, 7722840, 197354133, 5764942816, 189460961985, 6917588290044, 277765971072770, 12163275845132298, 576793897136731632, 29444368084753254610, 1609805318425385690712, 93843785859803533422675

Offset: 0

Author

Paul D. Hanna, Aug 23 2006

Keywords

• nonn

Comments

Also column 2 of square array A136737.

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: A121421, A121423.

Cf. A136737; A121413, A121417; A121427, A136741.

Programs

PARI

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

Extensions

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