It’s a beautiful day (Spring is here! Spring is here!) and time to go to the carnival! The Carnival of Mathematics #31 is hosted by Recursivity this week, and blog author Jeffrey Shallit notes that not only is 31 a Mersenne prime (because it’s of the form 2prime-1, in this case 25-1), but so is 231-1. (The pattern ends there, however, as he explains that 2(231-1)-1 is not a prime at all.)
Recursivity is a blog about mathematics, science, politics, music, and religion. I especially enjoyed this post on math mistakes last month (since that’s a running category in our own blog). Bonus points for having a Blog name that my spellcheck doesn’t recognize [HAH! It doesn’t recognize the word “spellcheck” either! ] [Or “HAH!”].