function [ n_data, x, fx ] = bessel_i0_values ( n_data )

%*****************************************************************************80
%
%% BESSEL_I0_VALUES returns some values of the I0 Bessel function.
%
%  Discussion:
%
%    The modified Bessel functions In(Z) and Kn(Z) are solutions of
%    the differential equation
%
%      Z^2 W'' + Z * W' - ( Z^2 + N^2 ) * W = 0.
%
%    The modified Bessel function I0(Z) corresponds to N = 0.
%
%    In Mathematica, the function can be evaluated by:
%
%      BesselI[0,x]
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    15 September 2004
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Milton Abramowitz and Irene Stegun,
%    Handbook of Mathematical Functions,
%    US Department of Commerce, 1964.
%
%    Stephen Wolfram,
%    The Mathematica Book,
%    Fourth Edition,
%    Wolfram Media / Cambridge University Press, 1999.
%
%  Parameters:
%
%    Input/output, integer N_DATA.  The user sets N_DATA to 0 before the
%    first call.  On each call, the routine increments N_DATA by 1, and
%    returns the corresponding data; when there is no more data, the
%    output value of N_DATA will be 0 again.
%
%    Output, real X, the argument of the function.
%
%    Output, real FX, the value of the function.
%
  n_max = 20;

  fx_vec = [ ...
     0.1000000000000000E+01, ...
     0.1010025027795146E+01, ...
     0.1040401782229341E+01, ...
     0.1092045364317340E+01, ...
     0.1166514922869803E+01, ...
     0.1266065877752008E+01, ...
     0.1393725584134064E+01, ...
     0.1553395099731217E+01, ...
     0.1749980639738909E+01, ...
     0.1989559356618051E+01, ...
     0.2279585302336067E+01, ...
     0.3289839144050123E+01, ...
     0.4880792585865024E+01, ...
     0.7378203432225480E+01, ...
     0.1130192195213633E+02, ...
     0.1748117185560928E+02, ...
     0.2723987182360445E+02, ...
     0.6723440697647798E+02, ...
     0.4275641157218048E+03, ...
     0.2815716628466254E+04 ];

  x_vec = [ ...
     0.00E+00, ...
     0.20E+00, ...
     0.40E+00, ...
     0.60E+00, ...
     0.80E+00, ...
     0.10E+01, ...
     0.12E+01, ...
     0.14E+01, ...
     0.16E+01, ...
     0.18E+01, ...
     0.20E+01, ...
     0.25E+01, ...
     0.30E+01, ...
     0.35E+01, ...
     0.40E+01, ...
     0.45E+01, ...
     0.50E+01, ...
     0.60E+01, ...
     0.80E+01, ...
     0.10E+02 ];

  if ( n_data < 0 )
    n_data = 0;
  end

  n_data = n_data + 1;

  if ( n_max < n_data )
    n_data = 0;
    x = 0.0;
    fx = 0.0;
  else
    x = x_vec(n_data);
    fx = fx_vec(n_data);
  end

  return
end
