“…The identity a 1 (n, m) = a 2 (m, n) for integers m, n > 0 becomes obvious after substituting ν → n − ν in a 1 (n, m), noticing that in both sums the summands are actually zero for ν > min(m, n). Since a 2 (n, m) = A(n, m) by ( 2), formula (4) follows from (6). Then, equation (7) holds for all integers x = n > 0 and also for all m > 0 due to the symmetry relation satisfied by p(n, m).…”