function L = graph_arc_petersen ( )

%*****************************************************************************80
%
%% graph_arc_petersen() sets up the arc list for the Petersen graph.
%
%  Discussion:
%
%    The graph has 10 nodes.
%    The graph has 15 edges or 30 arcs.
%
%  Licensing:
%
%    This code is distributed under the MIT license. 
%
%  Modified:
%
%    30 April 2026
%
%  Author:
%
%    John Burkardt
%
%  Output:
%
%    integer arc(arc_num,2): the arc list.  
%
  L = [ ...
    1,  2; ...
    1,  5; ...
    1,  6; ...
    2,  1; ...
    2,  3; ...
    2,  7; ...
    3,  2; ...
    3,  4; ...
    3,  8; ...
    4,  3; ...
    4,  5; ...
    4,  9; ...
    5,  1; ...
    5,  4; ...
    5, 10; ...
    6,  1; ...
    6,  7; ...
    6, 10; ...
    7,  2; ...
    7,  6; ...
    7,  8; ...
    7, 10; ...
    8,  3; ...
    8,  7; ...
    8, 10; ...
    9,  4; ...
   10,  5; ...
   10,  6; ...
   10,  7; ...
   10,  8 ];

  return
end
