OFFSET
0,2
PROG
(PARI) {a(n)=local(A=Mat(1), B); for(m=2, n+2, B=matrix(m, m); for(i=1, m, for(j=1, i, if(j==i, B[i, j]=1, if(j==1, B[i, j]=(A^-2)[i-1, 1], B[i, j]=(A^-2)[i-1, j]-(A^-2)[i-1, j-1])); )); A=B); return(A[n+2, 2])}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Jan 22 2005
STATUS
approved