Pyramid #694
Generating function
$$U_{694}(x, y) = \frac{1 - \sqrt{4 x \left(1 - \frac{4 \sin^{2}{\left(\frac{\operatorname{asin}{\left(\frac{3 \sqrt{3} \sqrt{- y}}{2} \right)}}{3} \right)}}{3}\right) + 1}}{2 x}$$
Explicit formula
$$T_{694}(n, m, k) = \begin{cases}\frac{\left(-1\right)^{- k + n} k {\binom{k + 2 n - 1}{k + n - 1}}}{k + n}&\text{if m=0} ,\ \\\frac{\left(-1\right)^{- k + n} \left(-1\right)^{m - 1} k {\binom{k + 2 n - 1}{k + n - 1}} {\binom{- k + 3 m - n - 1}{m - 1}}}{m}&\text{if m>0} \end{cases} $$
Data table
-1 -1 2 -7 30 -143 728
1 2 -3 1 -42 198 -1001
-2 -6 6 -2 84 -396 2002
5 2 -1 4 -175 84 -429
-14 -7 0 -7 35 -1764 924
42 252 126 84 -63 3528 -19404
-132 -924 -924 0 924 -6468 38808
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