Pyramid #471
Generating function
$$U_{471}(x, y) = \frac{\sqrt{4 y + 1}}{6} + \frac{\left(\sqrt{4 y + 1} + 1\right)^{2}}{36 \sqrt[3]{\frac{x}{\sqrt{4 y + 1} + 1} + \frac{\sqrt{3} \sqrt{x \left(27 x + \frac{\left(\sqrt{4 y + 1} + 1\right)^{4}}{4}\right)}}{9 \sqrt{4 y + 1} + 9} + \frac{\left(\sqrt{4 y + 1} + 1\right)^{3}}{216}}} + \sqrt[3]{\frac{x}{\sqrt{4 y + 1} + 1} + \frac{\sqrt{3} \sqrt{x \left(27 x + \frac{\left(\sqrt{4 y + 1} + 1\right)^{4}}{4}\right)}}{9 \sqrt{4 y + 1} + 9} + \frac{\left(\sqrt{4 y + 1} + 1\right)^{3}}{216}} + \frac{1}{6}$$
Explicit formula
$$T_{471}(n, m, k) = \begin{cases}1&\text{if n=0 and m=0} ,\ \\\frac{\left(-1\right)^{n - 1} k {\binom{- k + 3 n - 1}{n - 1}}}{n}&\text{if m=0} ,\ \\\frac{\left(-1\right)^{m - 1} k {\binom{- k + 2 m + n - 1}{m - 1}}}{m}&\text{if n=0} ,\ \\\frac{\left(-1\right)^{m - 1} k \left(k - 4 n\right) {\binom{k - 2 n - 1}{n - 1}} {\binom{- k + 2 m + 4 n - 1}{m - 1}}}{m n}&\text{if n>0 and m>0} \end{cases} $$
Data table
1 1 -1 2 -5 14 -42
1 -3 9 -28 9 -297 1001
-2 14 -7 308 -1274 5096 -19992
7 -77 539 -308 15708 -74613 337953
-3 45 -405 285 -17325 95634 -49335
143 -2717 29887 -249964 176605 -11126115 64531467
-728 16744 -217672 2109744 -1699516 120422848 -776519744
Export
expand_less