  The forward inclusive pion double charge exchange reaction,
^{16}O(pi^-,pi^+)X, at T_0 = 0.50 and 0.75 GeV has been studied in the
kinematical region where an additional pion production is forbidden by
energy-momentum conservation. The experiment was performed with the SKS
spectrometer at KEK PS. The measured ratio of double charge exchange
cross-section for these energies dsigma(0.50 GeV)/dOmega / dsigma(0.75
GeV)/dOmega = 1.7 +/- 0.2, disagrees with the value of 7.2 predicted within the
conventional sequential single charge exchange mechanism. Possible reasons for
the disagreement are discussed in connection with the Glauber inelastic
rescatterings.
