Bessel Polynomial (Not in Base Package)

Calculates the Bessel Polynomial of order n for any real number x. Details  

	x is any real number.
	n is the nonnegative order (integer) of the Bessel polynomial.
	Bessel polynomial (n,x) is the result of the calculation of the order n Bessel polynomial at the given value of x.

Bessel Polynomial Details

The following equation shows a recurrence relation that defines the Bessel polynomial P_n(x) of order n.

where P₀(x) = 1 and P₁(x) = 1 + x.

The following illustration shows the first four Bessel polynomials from bottom to top on the right side. The range of x is from [–6, 6].