Kelvin function Uncommon

Any of class of special functions, usually denoted as two pairs of functions berₙ(x), beiₙ(x), kerₙ(x) and keiₙ(x) with variable x and given order number n. The former two functions berₙ(x) and beiₙ(x) respectively correspond to the real part and the imaginary part of the Kelvin differential equation's solution that can be expressed with the Bessel function of the first kind Jₙ(x), and the latter kerₙ(x) and keiₙ(x) correspond to those that can be expressed with the modified Bessel function of the second kind Kₙ(x).