length 2: 12, 21
length 3: 123, 213, 231, 312, 321
length 4: 1234, 2134, 2341, 3241, 4123, 4213, 4231
length 5: 12345, 21345, 23451, 32451, 51234, 52134, 52341
$\mathcal{A}$ = Av(132, 2314, 3124, 3214, 3412, 3421, 4312, 4321)
$\mathcal{B}$ = Av(132, 312, 321, 2314)
$\mathcal{C}$ = Av(132, 231, 312, 321)
$\operatorname{F_{4}}{\left (x \right )} = \operatorname{F_{0}}{\left (x \right )} + \operatorname{F_{3}}{\left (x \right )}$
$\operatorname{F_{0}}{\left (x \right )} = 1$
$\operatorname{F_{3}}{\left (x \right )} = \operatorname{F_{1}}{\left (x \right )} + \operatorname{F_{2}}{\left (x \right )}$
$\operatorname{F_{1}}{\left (x \right )} = \frac{x}{x - 1} \left(- x^{3} - x^{2} - 1\right)$
$\operatorname{F_{2}}{\left (x \right )} = - \frac{x^{2} \left(x + 1\right)^{2}}{x - 1}$