Pyramid #838
Pyramid #839
Pyramid #840
Generating function
$$U_{839}(x, y) = \frac{x y - x - 1}{y^{3} - 3 y^{2} + 3 y - 1}$$
Explicit formula
$$T_{839}(n, m, k) = {\binom{k}{n}} {\binom{3 k + m - n - 1}{m}}$$
Data table
1 3 6 1 15 21 28
1 2 3 4 5 6 7
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0
Related
Pyramid #837: Right on x
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