\(\displaystyle \left(x -1\right) \left(2 x^{2}-4 x +1\right) \left(2 x -1\right)^{4} F \! \left(x \right)-6 x^{7}+58 x^{6}-168 x^{5}+218 x^{4}-152 x^{3}+59 x^{2}-12 x +1 = 0\)
Recurrence
\(\displaystyle a \! \left(0\right) = 1\) \(\displaystyle a \! \left(1\right) = 1\) \(\displaystyle a \! \left(2\right) = 2\) \(\displaystyle a \! \left(3\right) = 6\) \(\displaystyle a \! \left(4\right) = 22\) \(\displaystyle a \! \left(5\right) = 86\) \(\displaystyle a \! \left(6\right) = 336\) \(\displaystyle a \! \left(7\right) = 1282\) \(\displaystyle a \! \left(n +6\right) = -32 a \! \left(n \right)+128 a \! \left(n +1\right)-192 a \! \left(n +2\right)+144 a \! \left(n +3\right)-58 a \! \left(n +4\right)+12 a \! \left(n +5\right)-2, \quad n \geq 8\)
Explicit Closed Form
\(\displaystyle \left\{\begin{array}{cc}1 & n =0 \\ \frac{\left(12 \sqrt{2}+12\right) \left(1-\frac{\sqrt{2}}{2}\right)^{-n}}{96}+\frac{\left(-12 \sqrt{2}+12\right) \left(1+\frac{\sqrt{2}}{2}\right)^{-n}}{96}+2+\\\frac{\left(n^{3}-18 n^{2}+59 n -138\right) 2^{n}}{96} & \text{otherwise} \end{array}\right.\)
Heatmap
To create this heatmap, we sampled 1,000,000 permutations of length 300
uniformly at random. The color of the point \((i, j)\) represents how many
permutations have value \(j\) at index \(i\) (darker = more).
This specification was found using the strategy pack "Point And Row Placements" and
has 70 rules.