This document contains code to calculate the Simpson's index of overlap between two genes (CDK2 and CDK6) using PubMed publication counts. It makes API calls to NCBI to retrieve the individual and combined publication counts for the two genes, then calculates the Simpson's index as the proportion of shared publications out of the total for the smaller gene count. The code outputs the individual counts, combined count, and Simpson's index value of 0.4326 for CDK2 and CDK6.