A semi-oriented 2-variable knot polynomial defined by F_L(a, z) = a^(-w(L)) 〈 left bracketing bar L right bracketing bar 〉, where L is an oriented link diagram, w(L) is the writhe of L, left bracketing bar L right bracketing bar is the unoriented diagram corresponding to L, and 〈L〉 is the bracket polynomial. It was developed by Kauffman by extending the BLM/Ho polynomial Q to two variables, and satisfies F(1, x) = Q(x).