Pyramid #1020
Pyramid #1021
Pyramid #1022
Generating function
$$U_{1021}(x, y) = \frac{\left(x + 1\right)^{3}}{\left(1 - y\right)^{2}}$$
Explicit formula
$$T_{1021}(n, m, k) = {\binom{3 k}{n}} {\binom{2 k + m - 1}{m}}$$
Data table
1 2 3 4 5 6 7
3 6 9 12 15 18 21
3 6 9 12 15 18 21
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
Related
Pyramid #1034: Change x y
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