Generating function
$$U_{1275}(x, y) = \frac{2 y^{3} \left(1 - \sqrt{- \frac{x \left(1 - \sqrt{1 - 4 y}\right)^{3}}{2 y^{3}} + 1}\right)^{2}}{x^{2} \left(1 - \sqrt{1 - 4 y}\right)^{3}}$$
Explicit formula
$$T_{1275}(n, m, k) = \frac{6 k \left(k + n\right) {\binom{2 k + 2 n - 1}{n}} {\binom{3 k + 2 m + 3 n - 1}{m}}}{\left(2 k + n\right) \left(3 k + m + 3 n\right)}$$
Data table
1 3 9 28 9 297 1001
2 12 54 22 858 3276 12376
5 45 27 1365 63 2754 11628
14 168 126 7616 40698 201096 942172
42 63 567 399 24255 1338876 69069
132 2376 24948 200376 13662 833976 4702698
429 9009 108108 975975 7378371 49378329 302366064
Export
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