Nice analysis, it's basically just an alternating series that uses the inclusion exclusion principle. https://en.wikipedia.org/wiki/Inclusion%E2%80%93exclusion

Nice analysis, it's basically just an alternating series that uses the inclusion exclusion principle. https://en.wikipedia.org/wiki/Inclusion%E2%80%93exclusion_principle https://en.wikipedia.org/wiki/Inclusion%E2%80%93exclusion_pr...