Generating function
$$U_{1224}(x, y) = \frac{\frac{\sin{\left(\frac{\operatorname{asin}{\left(216 y^{2} - 1 \right)}}{3} \right)}}{6 y} + \frac{1}{12 y}}{\left(1 - x\right)^{3}}$$
Explicit formula
$$T_{1224}(n, m, k) = \begin{cases}1&\text{if n=0 , m=0 , k=0} ,\ \\\frac{4^{m} k {\binom{\frac{k}{2} + \frac{3 m}{2} - 1}{m}} {\binom{3 k + n - 1}{n}}}{k + m}&\text{if k even} ,\ \\\frac{k {\binom{\frac{k}{2} + \frac{3 m}{2} - \frac{1}{2}}{m}} {\binom{k + 3 m - 1}{\frac{k}{2} + \frac{3 m}{2} - \frac{1}{2}}} {\binom{3 k + n - 1}{n}}}{\left(k + m\right) {\binom{k + m - 1}{\frac{k}{2} + \frac{m}{2} - \frac{1}{2}}}}&\text{if k odd} \end{cases} $$
Data table
1 1.5 10 42 462 2252.25 29172
3 4.5 30 126 1386 6756.75 87516
6 9 60 252 2772 13513.5 175032
10 15 100 420 4620 22522.5 291720
15 22.5 150 630 6930 33783.75 437580
21 31.5 210 882 9702 47297.25 612612
28 42 280 1176 12936 63063 816816
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