When π is known (and hence μ), several statistical methods are available to compute S: exact computations [1-4], Gaussian [5,6], binomial [7,8], compound Poisson [9-11] or large deviations approximations [12]. But in general, the parameter π is not available and must be estimated. Let us denote by N0 (resp. N1) the (overlap) frequencies of all words of size m (resp. m + 1) in the sequence Y = Y1 ... Yn, then the Maximum-Likelihood Estimator (MLE) of π is given by