Pyramid #51
Generating function
$$U_{51}(x, y) = \frac{x y - \sqrt{x^{2} y^{2} + y \left(- 2 x - 4\right) + 1} + 1}{2 y}$$
Explicit formula
$$T_{51}(n, m, k) = \frac{k {\binom{k + m}{n}} {\binom{k + 2 m - n - 1}{m}}}{k + m}$$
Data table
1 1 2 5 14 42 132
1 1 3 1 35 126 462
0 0 1 6 3 14 63
0 0 0 1 1 7 42
0 0 0 0 1 15 14
0 0 0 0 0 1 21
0 0 0 0 0 0 1
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