User talk:2600:1700:3B20:73E0:D9F5:1ADC:A9ED:8638

Hello, I'm David Eppstein. I wanted to let you know that one or more of your recent contributions to List of unsolved problems in mathematics have been undone because they did not appear constructive. If you would like to experiment, please use the sandbox. If you have any questions, you can ask for assistance at the Help Desk. Thanks. —David Eppstein (talk) 01:18, 20 January 2019 (UTC)