For each model a sampling of 2 billion molecules was performed in epoch 70 (summing up to 50 billion molecules), repeated molecules were filtered and the whole sample was separated between molecules contained and not contained in GDB-13. Note that the number of molecules needed to sample from the ideal model to obtain 100% of the database on average is around 21 billion (Equation ), much less than the 50 billion molecules sampled in this experiment. The frequency for each molecule in GDB-13 was computed, which is the number of times from 0 (not sampled in any model) to 25 (sampled in all models) each molecule was uniquely sampled from each model. In the ideal model, each sample can be considered as a Bernoulli trial with 𝑝 = 0.8712 (see (Equation ), so the distribution of the frequency would follow a binomial distribution with 𝑛 = 25, 𝑘 = 2 • 10 9 and 𝑝 = 0.8712. Figure shows that the two distributions have a different mean (17.1 and 21.8) and mode and the distribution obtained from the RNN models has an extremely long tail. Moreover, 5,720,928 molecules (0.6 %) have never been sampled by any model. Notice also in Figure that frequency is heavily correlated with the average likelihood for each molecule obtained from every model.