  The doubly shortened perfect codes of length 13 are classified utilizing the
classification of perfect codes in [P.R.J. \"Osterg{\aa}rd and O. Pottonen, The
perfect binary one-error-correcting codes of length 15: Part I -
Classification, IEEE Trans. Inform. Theory, to appear]; there are 117821 such
(13,512,3) codes. By applying a switching operation to those codes, two more
(13,512,3) codes are obtained, which are then not doubly shortened perfect
codes.
