Pyramid #41
Generating function
$$U_{41}(x, y) = \frac{x}{2} + \frac{\sqrt{x^{2} + 2 x + 4 y + 1}}{2} + \frac{1}{2}$$
Explicit formula
$$T_{41}(n, m, k) = \begin{cases}1&\text{if n=0,m=0} ,\ \\\frac{k {\binom{m + n}{n}} {\binom{k - m - 1}{m + n - 1}}}{m + n} \end{cases} $$
Data table
1 1 -1 2 -5 14 -42
1 -1 3 -1 35 -126 462
0 1 -6 3 -14 63 -2772
0 -1 1 -7 42 -231 12012
0 1 -15 14 -105 693 -42042
0 -1 21 -252 231 -18018 126126
0 1 -28 42 -462 42042 -336336
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