“…By applying the rule that μ s,t is equal to the sum of the s-powers of the zeros of P −1 t (x) we find for the idempotent table M 20,3,−1 , the rows of which are indexed respectively by 0, 1, 2, 4, 11, 5 and the columns by 0, 2, 3, 6, 12, 5. For more examples of primitive idempotents of constacyclic and negacyclic codes we refer to [10,16,22,[26][27][28].…”