Fermat pseudoprimes mathworld.wolfram.com/FermatPseudopr…

The Fermat numbers F_0 thru F_4 are prime. Euler found that F_5 is composite.

Solving a cubic equation is generally messy, but this post shows it can be simple for a 'depressed' cubic with negative discriminant.
twitter.com/SciPyTip/statu…

Exponential sum 11-2-22

johndcook.com/expsum/

Fermat numbers have the form 2^{2^m} + 1.

Low rank matrix perturbations

johndcook.com/blog/2018/06/1…

VIN (Vehicle Identification Number) check sums johndcook.com/blog/2019/09/1…

Definition of pullbacks with examples

johndcook.com/blog/pullbacks/

A field is a ring in which non-zero elements form an abelian group under multiplication.

Ax’s Theorem: An Application of Logic to Ordinary Mathematics

xorshammer.com/2008/08/15/axs…

Introduction to rings and modules

youtu.be/4WmIDodIgac

Why can't programmers tell Halloween from Christmas?

Because oct 31 = dec 25.

(The joke worked better when programmers were more accustomed to octal.)

The final result of a sequence of A/B tests may depend on the order of your tests. How to do better.

johndcook.com/blog/2022/10/3…

The sum of the reciprocals of the primes diverges.

Last exponential sum of October

johndcook.com/expsum/

/via Mathematical Mathematics Memes

19 proofs that there are infinitely many primes

cjquines.com/files/infinite… [pdf]