code: def phi_n(self,n,x):
          
          prefactor = 1./np.sqrt(2**n*np.sqrt(np.pi)*math.factorial(n))
          return prefactor*self.H_n(n,x)*np.exp(-x**2/2.)
docs: constructs the 1-dim basis function (formula (1) in Refregier et al. 2001)
  
          :param n: The n'the basis function.
          :type name: int.
          :param x: 1-dim position (dimensionless)
          :type state: float or numpy array.
          :returns:  array-- phi_n(x).
          :raises: AttributeError, KeyError