%N Number of distinct critical exponents possible, over all binary strings of length n.
%C A string x has period p if x[i]=x[i+p] for all i that make sense. The shortest period is called "the" period. The exponent exp(x) of a string x of length n is defined to be n/p, where p is the period. The critical exponent of a string x is the maximum, over all nonempty contiguous subwords w of x, of exp(w).
%e For n = 6, there are 5 possible critical exponents: 6 (for 000000), 5 (for 000001), 4 (for 000011), 3 (for 000111), 2 (for 001001), and 5/2 (for 001010).
%A _Jeffrey Shallit_, Jul 23 2018