code: def F_4(x, n):
      assert_equal(n % 3, 0)
      g = np.zeros([n])
      # Note: the first line is typoed in some of the references;
      # correct in original [Gasparo, Optimization Meth. 13, 79 (2000)]
      g[::3] = (
          0.6 * x[::3]
          + 1.6 * x[1::3] ** 3
          - 7.2 * x[1::3] ** 2
          + 9.6 * x[1::3]
          - 4.8
      )
      g[1::3] = (
          0.48 * x[::3]
          - 0.72 * x[1::3] ** 3
          + 3.24 * x[1::3] ** 2
          - 4.32 * x[1::3]
          - x[2::3]
          + 0.2 * x[2::3] ** 3
          + 2.16
      )
      g[2::3] = 1.25 * x[2::3] - 0.25 * x[2::3] ** 3
      return g
  
imports: from __future__ import division, absolute_import, print_function
  import itertools
  import numpy
  from numpy import exp
  from numpy.testing import assert_, assert_equal
  from scipy.optimize import root
label_desc: Use image node_id 9 for calling a global function with example usage: F_4(x, n) and returns: g