Avoidability of circular formulas
نویسندگان
چکیده
Clark has defined the notion of n-avoidance basis which contains the avoidable formulas with at most n variables that are closest to be unavoidable in some sense. The family Ci of circular formulas is such that C1 = AA, C2 = ABA.BAB, C3 = ABCA.BCAB.CABC and so on. For every i 6 n, the n-avoidance basis contains Ci. Clark showed that the avoidability index of every circular formula and of every formula in the 3-avoidance basis (and thus of every avoidable formula containing at most 3 variables) is at most 4. We determine exactly the avoidability index of these formulas.
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ورودعنوان ژورنال:
- CoRR
دوره abs/1610.04439 شماره
صفحات -
تاریخ انتشار 2016