Computing RSA isn't that hard An overview how RSA and public-key cryptography in general work and a basic implementation of RSA in the Dart programming language.
Computing Advanced LMC A basic stack data type and factorial program implemented in LMC, a language with only 10 instructions.
Maths Shoelace formula An interesting formula to work out the area of a polygon given the coordinates of its points. Also known as Gauss's area formula.