PM Lee spending some vacation time on the Collatz conjecture: 5 things about the unsolved problem https://straitstimes.com/singapore/pm-lee-spending-some-vacation-time-on-the-collatz-conjecture-5-things-about-the-unsolved?utm_term=Autofeed&utm_campaign=sttw&utm_medium=social&utm_source=Twitter#Echobox=1576902443β¦