On the existence of a certain (64, 32, 12) extremal code

J.H. Conway and N.J.A. Sloane (see ibid., vol.36, no.6, p.1319-33, Nov. 1990) give weight enumerators of several self-dual codes with the highest possible minimal distance whose existence was not known. A generator matrix for one of these, a Type I (64, 32, 12) code, is given, proving its existence. The method of construction is described.<
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