OFFSET
0,2
COMMENTS
Triangular matrix T=A109152 satisfies: T(n,k) = [T^2](n-1,k) for n>k+1>=1, with T(n,n) = 1 and T(n+1,n) = n+1 for n>=0.
PROG
(PARI) {a(n)=local(M=matrix(n+1, n+1)); M=M^0; for(i=1, n, M=matrix(n+1, n+1, r, c, if(r>=c, if(r==c, 1, if(r==c+1, c, (M^2)[r-1, c]))))); return(sum(k=0, n, M[n+1, k+1]))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jun 20 2005
STATUS
approved