grandes-ecoles 2012 QII.C.4

grandes-ecoles · France · centrale-maths2__mp Sequences and Series Recurrence Relations and Sequence Properties
We consider the sequence $x = (x_n)_{n \geqslant 0}$ defined by $$x_0 = 1, \quad x_1 = 1, \quad x_2 = 1, \quad x_3 = 0, \quad \text{and} \quad \forall n \in \mathbb{N}, x_{n+4} = x_{n+3} - 2x_{n+1}$$
Give a formula allowing for any $n \geqslant 1$ to directly compute $x_n$.
We consider the sequence $x = (x_n)_{n \geqslant 0}$ defined by
$$x_0 = 1, \quad x_1 = 1, \quad x_2 = 1, \quad x_3 = 0, \quad \text{and} \quad \forall n \in \mathbb{N}, x_{n+4} = x_{n+3} - 2x_{n+1}$$

Give a formula allowing for any $n \geqslant 1$ to directly compute $x_n$.