Tag Archives: divisors

More fun with Dirichlet convolution

Posted on January 5, 2017 by Brent

I’m back after a bit of a hiatus for the holidays! Last time we saw how the principle of Möbius inversion arises from considering the function from the point of view of Dirichlet convolution. Put simply, the Möbius function is … Continue reading →

Posted in number theory | Tagged , , , , , , | 1 Comment

Fun with repunit divisors

Posted on November 11, 2011 by Brent

In honor of today’s date (11/11/11), here’s a fun little problem (and some follow-up problems) I’ve seen posed in a few places (for example, here is a very similar problem). If I recall correctly, it was also a problem on … Continue reading →

Posted in arithmetic, challenges, modular arithmetic, number theory, primes | Tagged , , | 16 Comments

Triangunit divisors

Posted on March 1, 2011 by Brent

Here’s a neat problem from Patrick Vennebush of Math Jokes 4 Mathy Folks: Append the digit 1 to the end of every triangular number. For instance, from 3 you’d get 31, and from 666 you’d get 6,661. Now take a … Continue reading →

Posted in number theory, pattern, puzzles | Tagged , , , , | 9 Comments