There’s a mathematical topic today on the New York Times’ Freakonomics blog. Their daily bleg (definition: using a blog to beg for information): What’s been said about math? Readers are invited to leave their favorite quotes about mathematics (or quotes by mathematicians) in the comments.

# Day: October 2, 2008

## Kuratowski’s closure-complement theorem (solution)

Stop! This post contains spoilers. This page has the solution to the problem posed in yesterday’s post. We challenged you to find a set from which we can make as many new sets as possible using only the closure and complement operations. In 1922 Kuratowski proved the following theorem. Theorem. At most 14 sets can…