Errata to the paper
T.H. Koornwinder, Dual addition formulas associated with dual product formulas,
in: Frontiers in Orthogonal Polynomials and q-Series, World Scientific, 2018,
Ch. 19, pp. 373-392; arXiv:1607.06053v5 [math.CA].
In formula (5.8) in the dennominator of the first fraction $n!$ should ve replaced by $j!$.
This has been corrected in the last arXiv version v5.