Where 𝐻 𝑛 is the n-th harmonic number and 𝛾 is the Euler-Mascheroni constant. By fitting this to the GDB-13 we would need to sample on average 20,761,554,747 SMILES. In the case of a non-uniform distribution, the previous number is a lower bound of 𝐸[𝑇], and the upper bound is the following: