bessel function

mybessel.py

def bessel_series(x, order):
    if order == 1:
        return 1

    sign = 1
    if (order % 2) == 0:
        sign = -1

    top = x ** ((order * 2) -2 )
    bottom = 1
    for i in range(1,order):
        bottom = bottom * (( i * 2)  ** 2)

    return sign * (top / bottom)

def bessel(x, order=10):
    temp = bessel_series(1,1)
    for i in range(2, order):
        temp += bessel_series(x,i)

    return temp


print(bessel(1.2))