1549. - Carnival

This week they are published posts with mathematical content as part of the second edition Mathematical Carnival. The idea is that they order me the link for mail, or the posteen here, and on Monday I will publish the different contributions.

Closing date: 14/3 (let's write it 3/14, the famous day of pi)

The previous week regretted without having been more active, what we are going to do to him.