Choose any sequence \$a_n\$ that has the following properties: \$a_n\$ is prime for all \$n\$; \$a_n\$ is strictly increasing; \$a_n\$ has an infinite number of terms; \$a_n\$ is sparse with respect to the primes. For the purposes of this question, we will define sparseness as follows: let \$A(...

Circumference of an ellipse code-golf math geometry Challenge Unlike the circumference of a circle (which is as simple as \$2\pi r\$), the circumference of an ellipse is hard. Given the semi-major axis \$a\$ and semi-minor axis \$b\$ of an ellipse (see the image below, from Wikipedia), calculate ...

50-100 rep for good answers in interesting new languages This is a bit subjective of course, but here are my criteria: The language is fairly new, and is interesting (in my opinion) The answer is clever, shows a lot of work put in, and shows off many features of the language (so no trivial posts...

Solve 4x4 Mastermind in exactly 5 steps code-golf puzzle-solver Background Mastermind is a game of code-breaking for two players. One of the players is codemaker (Alice) and the other is codebreaker (Bob). 4x4 means that the player should guess the length-4 sequence made of four alphabets (say RG...

The Xerox Alto, originally released in 1973, was the first computer to feature the now-familiar angled mouse pointer. The Alto's bitmapped pointer looked like this (redrawn from Fig. 2 here): Your task in this code-golf challenge is to write a program/function that generates an ASCII art represe...

Deserialize a binary tree breadth-first The task here is to deserialize a binary tree breadth-first. You probably know how to do that already, but here's an example: Input: [1, 5, 3, #, 4, 10, 2] Tree List: [5, 3, #, 4, 10, 2] 1 Tree List: [3, #, 4, 1...

Peel away the layers Meta: A rework of this proposal In this cops-and-robbers challenge, robbers must work together in order to crack cop answers by finding out which languages the cops used. Cops You are to write a program, which, when executed in a specific language, does one of the following:...

I guess you could call this the next challenge in the "Irreducible series". Hello World Challenge Create a cat subject to the constraint that it is irreducible. A cat program C is considered irreducible if there does not exist a cat (in the same programming language as C) that can be constructe...