fibonacci <- function ( n )

#*****************************************************************************80
#
## fibonacci returns the n-th item in the Fibonacci sequence.
#
#  Licensing:
#
#    Copyright 2016 James P. Howard, II
#
#    The computer code and data files on this web page are distributed under
#    https://opensource.org/licenses/BSD-2-Clause, the BSD-2-Clause license.
#
#  Modified:
#
#    14 January 2020
#
#  Author:
#
#    Original R version by James Howard.
#    Modifications by John Burkardt.
#
#  Reference:
#
#    James Howard,
#    Computational Methods for Numerical Analysis with R,
#    CRC Press, 2017
#    ISBN13: 978-1-4987-2363-3.
#
#  Input:
#
#    real N, the index of the item.
#    0 <= N.
#
#  Output:
#
#    real VALUE, the value of the n-th item.
{
  if ( n == 0 )
    return ( 0 )
  if ( n == 1 )
    return ( 1 )
  return ( fibonacci ( n - 1 ) + fibonacci ( n - 2 ) )
}