Av(132, 213, 231, 4312)

Permutation examples

length 2: 12, 21

length 3: 123, 312, 321

length 4: 1234, 4123, 4321

length 5: 12345, 51234, 54321

ATRAP tree (size 5, depth 3)

Legend

$\mathcal{A}$ = Av(132, 213, 231, 4312)

$\mathcal{B}$ = Av(21)

$\mathcal{C}$ = Av(132, 213, 231, 312)

Generating function

$A(x) = - \frac{x^{3} + x^{2} + 1}{x - 1}$

Coefficients

1, 1, 2, 3, 3, 3, 3, 3, 3, 3, 3, ...

System of equations

$\operatorname{F_{4}}{\left (x \right )} = \operatorname{F_{0}}{\left (x \right )} + \operatorname{F_{3}}{\left (x \right )}$

$\operatorname{F_{0}}{\left (x \right )} = 1$

$\operatorname{F_{3}}{\left (x \right )} = \operatorname{F_{1}}{\left (x \right )} + \operatorname{F_{2}}{\left (x \right )}$

$\operatorname{F_{1}}{\left (x \right )} = - \frac{x}{x - 1}$

$\operatorname{F_{2}}{\left (x \right )} = x \left(-1 + \frac{- x^{2} - 1}{x - 1}\right)$