OFFSET
0,2
PROG
(PARI) {a(n)=local(A=Mat(1), B); for(m=2, n+1, B=matrix(m, m); for(i=1, m, for(j=1, i, if(j==i, B[i, j]=1, B[i, j]=-j*(A^-1)[i-j, 1]); )); A=B); return(Vec(Ser(vector(n+1, i, (A^-1)[i, 1]))^2)[n+1])}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Oct 06 2005
STATUS
approved