function [ n_data, x, fx ] = debye3_values ( n_data )

%% DEBYE3_VALUES returns some values of Debye's function of order 3.
%
%  Discussion:
%
%    The function is defined by:
%
%      DEBYE3(x) = 3 / x^3 * Integral ( 0 <= t <= x ) t^3 / ( exp ( t ) - 1 ) dt
%
%    The data was reported by McLeod.
%
%  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 = [ ...
      0.99926776885985461940E+00, ...
      0.98833007755734698212E+00, ...
      0.95390610472023510237E+00, ...
      0.82496296897623372315E+00, ...
      0.67441556407781468010E+00, ...
      0.54710665141286285468E+00, ...
      0.44112847372762418113E+00, ...
      0.35413603481042394211E+00, ...
      0.28357982814342246206E+00, ...
      0.18173691382177474795E+00, ...
      0.16277924385112436877E+00, ...
      0.11759741179993396450E+00, ...
      0.95240802723158889887E-01, ...
      0.77581324733763020269E-01, ...
      0.36560295673194845002E-01, ...
      0.19295765690345489563E-01, ...
      0.57712632276188798621E-02, ...
      0.24352200674805479827E-02, ...
      0.72154882216335666096E-03, ...
      0.15585454565440389896E-03 ];

  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