Bessel function I(n,z)

is the solution of the modified Bessel equation which is zero at z=0 (for n>0, I(0, 0) = 1 ) and has the following behavior at positive infinity:

It admits the following integral representation:

n-index, z-argument 
 MathMate syntax:            I(n,z) 
 Domain:                     n an integer, z any real number