function c = catalan ( n )

%*****************************************************************************80
%
%% catalan() computes the Catalan numbers, from C(0) to C(N).
%
%  First values:
%
%     C(0)     1
%     C(1)     1
%     C(2)     2
%     C(3)     5
%     C(4)    14
%     C(5)    42
%     C(6)   132
%     C(7)   429
%     C(8)  1430
%     C(9)  4862
%    C(10) 16796
%
%  Formula:
%
%    C(N) = (2*N)! / ( (N+1) * (N!) * (N!) )
%         = 1 / (N+1) * COMB ( 2N, N )
%         = 1 / (2N+1) * COMB ( 2N+1, N+1).
%
%  Recursion:
%
%    C(N) = 2 * (2*N-1) * C(N-1) / (N+1)
%    C(N) = sum ( 1 <= I <= N-1 ) C(I) * C(N-I)
%
%  Discussion:
%
%    The Catalan number C(N) counts:
%
%    1) the number of binary trees on N vertices;
%    2) the number of ordered trees on N+1 vertices;
%    3) the number of full binary trees on 2N+1 vertices;
%    4) the number of well formed sequences of 2N parentheses;
%    5) number of ways 2N ballots can be counted, in order,
%       with N positive and N negative, so that the running sum
%       is never negative;
%    6) the number of standard tableaus in a 2 by N rectangular Ferrers diagram;
%    7) the number of monotone functions from [1..N} to [1..N} which
%       satisfy f(i) <= i for all i;
%    8) the number of ways to triangulate a polygon with N+2 vertices.
%
%  Example:
%
%    N = 3
%
%    ()()()
%    ()(())
%    (()())
%    (())()
%    ((()))
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    04 June 2004
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Dennis Stanton, Dennis White,
%    Constructive Combinatorics,
%    Springer Verlag, New York, 1986.
%
%  Input:
%
%    integer N, the number of Catalan numbers desired.
%
%  Output:
%
%    integer C(1:N+1), the Catalan numbers from C(0) to C(N).
%
  if ( n < 0 )
    c = [];
    return;
  end

  c(1) = 1;
%
%  The extra parentheses ensure that the integer division is
%  done AFTER the integer multiplication.
%
  for i = 1 : n
    c(i+1) = ( c(i) * 2 * ( 2 * i - 1 ) ) / ( i + 1 );
  end

  return
end
