Hi, I believe that arguments in this condition: https://github.com/JuliaMath/Bessels.jl/blob/fa3a1cb3376fb47177c8e09252d0e73385762478/src/BesselFunctions/besseli.jl#L626 should be reversed, ie `Math.check_convergence(s, t) && break` Currently the loop spins 3k times causing slow evaluation.