I stumbled upon the sequence $$1, 1, 2, 1, 1, 0, 1, 1, 2, 1, 1, 0, 1, 1, 2, 1, 1, 0, 1, 1, 2, 1, 1, 0, 1, 1, 2, 1, 1, 0, 1, 1, 2, 1, 1, 0, 1, 1, 2, 1, 1, 0, 1, 1, 2, 1, 1, 0,...$$ which is the sequence https://oeis.org/A173432 and I was wondering what NW-SE diagonal sums of Riordan arrays are. I tried to deduce from the definition of the Riordan array https://en.wikipedia.org/wiki/Riordan_array but I was not really succesful and google search gave me the impression that it simply means something related to the "direction of summation" but I am lacking a definition with gives me the integer sequence https://oeis.org/A173432.
Does anyone have the definition for me and how the sequence is derived from Riordan arrays?