Hermite polynomial : hermite

### 2.26.2 Hermite polynomial : `hermite`

`hermite` takes as argument an integer n and optionnally a variable name (by default x).
`hermite` returns the Hermite polynomial of degree n.
If H(n,x) denotes the Hermite polynomial of degree n, the following recurrence relation holds:

H(0,x)=1, H(1,x)=2x, H(n,x)=2xH(n−1,x)−2(n−1)H(n−2,x)

These polynomials are orthogonal for the scalar product:

<f,g>= | ∫ |
+∞
−∞
| f(x)g(x)e−x2dx

Input :

`hermite(6)`

Output :

`64*x```^```6+-480*x```^```4+720*x```^```2-120`

Input :

`hermite(6,y)`

Output :

`64*y```^```6+-480*y```^```4+720*y```^```2-120`