OFFSET
0,2
COMMENTS
PROG
(PARI) {a(n)=local(A=Mat(1), B); for(m=1, n+1, 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^2)[n+1, 1])}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Aug 22 2006, Jan 19 2008
EXTENSIONS
Edited by N. J. A. Sloane, Oct 30 2008 at the suggestion of R. J. Mathar
STATUS
approved