A121392 Column 1 of triangle A121391, where column k of T=A121391 equals column k of T^(k+1) shift down 1 row.

1, 1, 2, 5, 15, 55, 252, 1449, 10305, 88611, 901204, 10642707, 143771206, 2194484737, 37458097842, 708733666387, 14751543118320, 335523928599914, 8290931998724535, 221426442466072303, 6362084485200488267

Offset

0,3

Comments

Also equal to column 1 (shifted 1 place) of the matrix square of triangle A121391.

Links

Table of n, a(n) for n=0..20.

Prog

(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^j)[i-1, j]); )); A=B); return(A[n+2, 2])}

Crossrefs

Cf. A121391 (triangle), A121393 (column 2), A121394 (column 3).

Sequence in context: A242275 A363200 A137533 * A216388 A005976 A351158

Adjacent sequences: A121389 A121390 A121391 * A121393 A121394 A121395

Keyword

nonn

Author

Paul D. Hanna, Jul 27 2006

Status

approved