A121423 Column 2 of triangle A121420.

1, 3, 18, 169, 2190, 36360, 737051, 17645187, 487025244, 15219471545, 530951735025, 20447695079658, 861389893507518, 39394187817328680, 1943446826192453505, 102863050524539640435, 5813722327999905078450

Offset: 0

Author

Paul D. Hanna, Aug 23 2006

Keywords

• nonn

Comments

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, A121422.

Programs

PARI

{a(n)=local(A=Mat(1), B); for(m=1, n+3, 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+3, 3])}