A121392 - OEIS

A121392

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

%I #3 Mar 30 2012 18:36:58

%S 1,1,2,5,15,55,252,1449,10305,88611,901204,10642707,143771206,

%T 2194484737,37458097842,708733666387,14751543118320,335523928599914,

%U 8290931998724535,221426442466072303,6362084485200488267

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

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

%o (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])}

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

%K nonn

%O 0,3

%A _Paul D. Hanna_, Jul 27 2006