Bessel function syntax in Maxima

The commands for Bessel functions in Maxima are:

Bessel function 1st kind: \( J_n \left( x \right) \)

bessel_j (index, expr)

Bessel function 2nd kind: \( Y_n \left( x \right) \)

bessel_y (index, expr)

Modified Bessel function 1st kind: \( I_n \left( x \right) \)

bessel_i (index, expr)

Modified Bessel function 2nd kind: \( K_n \left( x \right) \)

bessel_k (index, expr)

http://maxima.sourceforge.net/docs/manual/en/maxima_15.html