Generating function
$$U_{1323}(x, y) = \frac{4096 y^{30} \left(- \frac{x \left(- 2 y - \sqrt{1 - 4 y} + 1\right)^{3}}{4 y^{6}} - \sqrt{- \frac{x \left(- 2 y - \sqrt{1 - 4 y} + 1\right)^{3}}{2 y^{6}} + 1} + 1\right)^{3}}{x^{6} \left(- 2 y - \sqrt{1 - 4 y} + 1\right)^{15}}$$
Explicit formula
$$T_{1323}(n, m, k) = \frac{9 k \left(k + n\right) {\binom{6 k + 2 n}{n}} {\binom{6 k + 2 m + 6 n}{m}}}{\left(3 k + n\right) \left(3 k + m + 3 n\right)}$$
Data table
1 6 27 11 429 1638 6188
6 72 54 3264 17442 86184 403788
27 486 5103 40986 27945 170586 9619155
11 264 3564 35728 29667 2160576 14283808
429 1287 212355 255255 24999975 211714074 160745871
1638 58968 1149876 1611792 181931022 1757187432 15075552492
6188 259896 584766 93649192 1197080976 1298960208 12430327546
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