OFFSET
1,4
COMMENTS
a(n) appears to be divisible by (n-1)(n-2)/2 for n>2.
EXAMPLE
exp(x) = (1 + 1*x + 1*x^2/2!) * (1 + 1*x^3/3! - 3*x^4/4!) * (1 + 6*x^5/5! + 10*x^6/6!) * (1 - 195*x^7/7! + 945*x^8/8!) *...
PROG
(PARI) {a(n)=if(n<1, 0, n!*polcoeff(exp(x +x*O(x^n))/prod(k=1, (n-1)\2, 1+a(2*k-1)*x^(2*k-1)/(2*k-1)!+a(2*k)*x^(2*k)/(2*k)! +x*O(x^n)), n))}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Feb 23 2008
STATUS
approved