A121393 - OEIS

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

%S 1,1,3,12,58,333,2268,18281,173127,1905500,24080964,345381551,

%T 5563259860,99716732043,1973012968122,42792555114812,1011125250589597,

%U 25886430637780776,714600877541340733,21178498962170286988

%N Column 2 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 2 (shifted 1 place) of the matrix cube of triangle A121391.

%o (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^j)[i-1, j]); )); A=B); return(A[n+3, 3])}

%Y Cf. A121391 (triangle), A121392 (column 1), A121394 (column 3).

%K nonn

%O 0,3

%A _Paul D. Hanna_, Jul 27 2006