Pyramid #849
Generating function
$$U_{849}(x, y) = \frac{1}{x y^{7} - 7 x y^{6} + 21 x y^{5} - x + y^{4} \left(1 - 35 x\right) + y^{3} \left(35 x - 4\right) + y^{2} \left(6 - 21 x\right) + y \left(7 x - 4\right) + 1}$$
Explicit formula
$$T_{849}(n, m, k) = {\binom{k + n - 1}{n}} {\binom{4 k + m - 3 n - 1}{m}}$$
Data table
1 4 1 2 35 56 84
1 1 1 1 1 1 1
1 -2 1 0 0 0 0
1 -5 1 -1 5 -1 0
1 -8 28 -56 7 -56 28
1 -11 55 -165 33 -462 462
1 -14 91 -364 1001 -2002 3003
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