function [ n_data, x, fx ] = bessel_i0_int_values ( n_data )

%*****************************************************************************80
%
%% BESSEL_I0_INT_VALUES returns some values of the Bessel I0 integral.
%
%  Discussion:
%
%    The function is defined by:
%
%      I0_INT(x) = Integral ( 0 <= t <= x ) I0(t) dt
%
%    The data was reported by McLeod.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    15 September 2004
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Allan McLeod,
%    Algorithm 757, MISCFUN: A software package to compute uncommon
%      special functions,
%    ACM Transactions on Mathematical Software,
%    Volume 22, Number 3, September 1996, pages 288-301.
%
%  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 = [ ...
      0.19531256208818052282E-02, ...
     -0.39062549670565734544E-02, ...
      0.62520348032546565850E-01, ...
      0.12516285581366971819E+00, ...
     -0.51051480879740303760E+00, ...
      0.10865210970235898158E+01, ...
      0.27750019054282535299E+01, ...
     -0.13775208868039716639E+02, ...
      0.46424372058106108576E+03, ...
      0.64111867658021584522E+07, ...
     -0.10414860803175857953E+08, ...
      0.44758598913855743089E+08, ...
     -0.11852985311558287888E+09, ...
      0.31430078220715992752E+09, ...
     -0.83440212900794309620E+09, ...
      0.22175367579074298261E+10, ...
      0.58991731842803636487E+10, ...
     -0.41857073244691522147E+11, ...
      0.79553885818472357663E+12, ...
      0.15089715082719201025E+17 ];

  x_vec = [ ...
       0.0019531250E+00, ...
      -0.0039062500E+00, ...
       0.0625000000E+00, ...
       0.1250000000E+00, ...
      -0.5000000000E+00, ...
       1.0000000000E+00, ...
       2.0000000000E+00, ...
      -4.0000000000E+00, ...
       8.0000000000E+00, ...
      18.0000000000E+00, ...
     -18.5000000000E+00, ...
      20.0000000000E+00, ...
     -21.0000000000E+00, ...
      22.0000000000E+00, ...
     -23.0000000000E+00, ...
      24.0000000000E+00, ...
      25.0000000000E+00, ...
     -27.0000000000E+00, ...
      30.0000000000E+00, ...
      40.0000000000E+00 ];  

  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
