Tag Archives: combinatorics

Fermat’s Little Theorem: proof by group theory

Posted on December 21, 2017 by Brent

It’s time for our third and final proof of Fermat’s Little Theorem, this time using some group theory. This proof is probably the shortest—explaining this proof to a professional mathematician would probably take only a single sentence—but requires you to … Continue reading →

Posted in group theory, number theory, primes, proof | Tagged , , , , | Comments Off on Fermat’s Little Theorem: proof by group theory

Fermat’s Little Theorem: proof by necklaces

Posted on December 12, 2017 by Brent

It’s time for our second proof of Fermat’s Little Theorem, this time using a proof by necklaces. As you know, proof by necklaces is a very standard technique for… wait, what do you mean, you’ve never heard of proof by … Continue reading →

Posted in combinatorics, number theory, primes, proof | Tagged , , , , , , | 4 Comments

Making our equation count

Posted on March 3, 2012 by Brent

[This is post #4 in a series; previous posts can be found here: Differences of powers of consecutive integers, Differences of powers of consecutive integers, part II, Combinatorial proofs.] We’re still trying to find a proof of the equation which … Continue reading →

Posted in combinatorics, pictures | Tagged , , , , | 3 Comments

Distributing cookies: solutions

Posted on April 14, 2009 by Brent

And now for some solutions to the cookie distribution problem. I’m actually going to describe four different methods of solution, and thereby (re)discover some nice combinatorial identities along the way. This is what I love about combinatorics—you discover all this … Continue reading →

Posted in counting, proof, solutions | Tagged , , , , , | 4 Comments

Distributing cookies

Posted on April 1, 2009 by Brent

Here’s a neat problem I saw in a recent post by Steven Miller on the Williams College math department blog. The problem comes from an old Putnam competition, one of the most prestigious college mathematics competitions. (It’s also one of … Continue reading →

Posted in challenges, counting | Tagged , , | 23 Comments