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
$$T_{1275}(n, m, k) = \frac{6 k \left(k + n\right) {\binom{2 k + 2 n - 1}{n}} {\binom{3 k + 2 m + 3 n - 1}{m}}}{\left(2 k + n\right) \left(3 k + m + 3 n\right)}$$
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 |
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