Coefficients in the asymptotic expansion for the product of modified Bessel functions $I_0(z) K_0(z)$

Question

I am interested in the coefficients for the general term in the asymptotic expansion of $ I_0(z) K_0(z)$. Abramowitz and Stegun (Equation 9.7.5) and all other available sources give the first two terms with the reference to Equation 9.2.28 for the development of the general term. Unfortunately also that formula is not quite clear: should the term with $ (2x)^8 $ in the denominator contain $ \frac{1\cdot 3 \cdot 5 \cdot 7}{2 \cdot 4 \cdot 6 \cdot 8} $ or $ \frac{1\cdot 3 \cdot 5 \cdot 7}{2 \cdot 4 \cdot 6 \cdot 24} $ ? Where can one find the explicit form for the general term?