OFFSET
0,2
FORMULA
PROG
(PARI) {a(n)=local(X=x+x^2*O(x^n), Y=y+y^2*O(y^n)); (matrix(n+2, n+2, m, k, if(m>=k, (m-1)!*polcoeff(polcoeff(exp(X+Y*X^2/2+X*Y), m-1, x), k-1, y)))^-1)[n+2, 2]}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, May 21 2005
STATUS
approved