code: def greenhall_BasicSum(J, M, S, F, alpha, d):
      
      first = pow(greenhall_sz(0, F, alpha, d), 2)
      second = (1-float(J)/float(M))*pow(greenhall_sz(float(J)/float(S), F, alpha, d), 2)
      third = 0
      for j in range(1, int(J)):
          third += 2*(1.0-float(j)/float(M))*pow(greenhall_sz(float(j)/float(S), F, alpha, d), 2)
      return first+second+third
docs: Eqn (10) from Greenhall2004