function [ n_data, x, fx ] = debye2_values ( n_data )

%*****************************************************************************80
%
%% DEBYE2_VALUES returns some values of Debye's function of order 2.
%
%  Discussion:
%
%    The function is defined by:
%
%      DEBYE2(x) = 2 / x^2 * Integral ( 0 <= t <= x ) t^2 / ( exp ( t ) - 1 ) dt
%
%    The data was reported by McLeod.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    16 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 = [ ...
      0.99934911727904599738E+00, ...
      0.98962402299599181205E+00, ...
      0.95898426200345986743E+00, ...
      0.84372119334725358934E+00, ...
      0.70787847562782928288E+00, ...
      0.59149637225671282917E+00, ...
      0.49308264399053185014E+00, ...
      0.41079413579749669069E+00, ...
      0.34261396060786351671E+00, ...
      0.24055368752127897660E+00, ...
      0.22082770061202308232E+00, ...
      0.17232915939014138975E+00, ...
      0.14724346738730182894E+00, ...
      0.12666919046715789982E+00, ...
      0.74268805954862854626E-01, ...
      0.47971498020121871622E-01, ...
      0.21369201683658373846E-01, ...
      0.12020564476446432799E-01, ...
      0.53424751249537071952E-02, ...
      0.19232910450553508562E-02 ];

  x_vec = [ ...
       0.0019531250E+00, ...
       0.0312500000E+00, ...
       0.1250000000E+00, ...
       0.5000000000E+00, ...
       1.0000000000E+00, ...
       1.5000000000E+00, ...
       2.0000000000E+00, ...
       2.5000000000E+00, ...
       3.0000000000E+00, ...
       4.0000000000E+00, ...
       4.2500000000E+00, ...
       5.0000000000E+00, ...
       5.5000000000E+00, ...
       6.0000000000E+00, ...
       8.0000000000E+00, ...
      10.0000000000E+00, ...
      15.0000000000E+00, ...
      20.0000000000E+00, ...
      30.0000000000E+00, ...
      50.0000000000E+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
