BESSELITILDE is the jOceans module of jLab.

 BESSELITILDE  I-type Bessel function after factoring off exponential growth.
 
    ITILDE=BESSELITILDE(NU,Z) returns the modified Bessel function of the
    first kind of order NU at argument Z, after factoring off the  
    asymptotic behavior of EXP(Z).
 
    BESSELITILDE is useful for products of modified Bessel functions in
    which the exponential behaviors cancel, but that cannot be evaluated
    directly because of numerical overflow.
 
    BESSELITILDE(NU,Z,N) use a summation truncated at N terms. The default
    behavior uses N=30 and is highly accurate.
 
    See 10.40.1 of https://dlmf.nist.gov/10.40.
 
    This is low-level code used by WINDTRANS using an algorithm described 
    in Lilly and Elipot (2021).
 
    See also BESSELKTILDE.
 
    'besselitilde --t' runs a test.
 
    Usage: I=besselitilde(nu,z);
           I=besselitilde(nu,z,nterms);
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    This is part of JLAB --- type 'help jlab' for more information
    (C) 2019--2021 J.M. Lilly --- type 'help jlab_license' for details