The article investigates the structural entropy of sequences that are fragmented into binary subsequences (symbols) of a given length, based on the frequency of these symbols in the total sequence. The sequences generated by the logistic mapping with the initial value of the sequences from the interval [0;1] and the step 0.1 are investigated. The maximum length of a symbol (subsequence) is 10 bits. A comparison of the calculated entropy values with its maximum value shows that there is a deviation from a uniform distribution for symbols with a length of 8 or more bits, but the entropy value gradually approaches the maximum with an increase in the length of the subsequence. It is also established that such a generation parameter as the initial value does not affect the entropy. The conducted studies also show that the algorithm is effective in terms of high speed and does not require the use of significant computing power.